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MITO Light Auto L3 study materials
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MITO Light Auto L3 practice questions

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Question 1Workshop safety, tools and environmental procedures

When using a bench grinder in the workshop, which eye protection is appropriate?

  1. Tinted sunglasses for glare
  2. Prescription glasses without side shields
  3. Safety goggles rated for impact Correct answer.
  4. No eye protection when the guard is fitted

Explanation

Impact-rated eye protection is required because grinding can throw metal fragments and abrasive particles toward the face. Prescription glasses and sunglasses are not impact-rated unless they are made as safety eyewear.

Question 2Workshop safety, tools and environmental procedures

Before using a hammer, what should a technician check?

  1. That the head is secure and the handle is sound Correct answer.
  2. That the face is painted a bright colour for visibility
  3. That the handle is deliberately loose for flexibility
  4. That the claw is sharpened to a fine point before use

Explanation

A hammer head must be firmly fixed to an undamaged handle so it cannot fly off during a strike. Cracked handles or loose heads should be taken out of service.

Question 3Workshop safety, tools and environmental procedures

Which extinguisher is suitable for a small petrol fire?

  1. A water extinguisher
  2. A foam extinguisher Correct answer.
  3. A water mist extinguisher
  4. A wet chemical extinguisher

Explanation

Petrol is a flammable liquid, so a foam extinguisher is suitable because it blankets the fuel and helps prevent re-ignition. Water-based extinguishers can spread flammable liquids and are not the correct choice for this fire class.

Question 4Workshop safety, tools and environmental procedures

After raising a vehicle with a trolley jack, what is the next safe step?

  1. Keep the jack raised and work quickly underneath
  2. Put blocks under the bumper and start work
  3. Place jack stands under the recommended points Correct answer.
  4. Lower the jack and rely on the vehicle wheels for support

Explanation

A trolley jack is for lifting, not for supporting a vehicle while someone works underneath it. Jack stands must be placed at the manufacturer's recommended lifting points before any work begins.

Question 5Workshop safety, tools and environmental procedures

What information does a safety data sheet provide for a workshop chemical?

  1. The torque setting stamped on the chemical drum
  2. Hazards, safe handling, and emergency steps Correct answer.
  3. The resale price of the chemical container
  4. The vehicle service interval for the workshop van

Explanation

A safety data sheet gives the hazard classification, safe handling precautions, first-aid measures, and spill response for a chemical. Technicians should consult it before using an unfamiliar product.

Question 6Workshop safety, tools and environmental procedures

How should used engine oil be handled?

  1. Burned in an open drum in the yard
  2. Mixed with general workshop rubbish
  3. Poured into the sanitary drain with water
  4. Stored in a labelled recycling container Correct answer.

Explanation

Used engine oil is a controlled waste and must be kept separate in a clearly labelled container for recycling or authorised collection. Pouring it into drains or burning it openly causes pollution and is unsafe.

Question 7Workshop safety, tools and environmental procedures

What is a safe practice when using compressed air for cleaning?

  1. Blow air toward other workers nearby
  2. Use low pressure with eye protection Correct answer.
  3. Use full pressure to clean bearings
  4. Direct the nozzle at skin to dry it quickly

Explanation

Compressed air can drive particles into the eyes or skin and can cause serious injury if directed at the body. Low pressure, eye protection, and safe nozzle direction reduce the risk.

Question 8Workshop safety, tools and environmental procedures

What is the correct practice when storing a torque wrench after use?

  1. Immerse it in oil to prevent rust
  2. Use it as a breaker bar for stubborn bolts
  3. Leave it at the last torque setting used
  4. Set it to its lowest marked setting Correct answer.

Explanation

A torque wrench should be stored at its lowest marked setting, or at zero if the manufacturer specifies, to avoid loading the spring unnecessarily. It should not be used as a breaker bar because that can damage its calibration.

Question 9Workshop safety, tools and environmental procedures

When using an angle grinder, what should be checked about the disc?

  1. That the disc is used without the side handle
  2. That the disc is rated for the grinder speed Correct answer.
  3. That the disc is larger than the fitted guard
  4. That the disc has no guard fitted at all

Explanation

The disc speed rating must be at least as high as the grinder speed so that it does not burst from overspeed. The guard and side handle should also be fitted as intended by the manufacturer.

Question 10Workshop safety, tools and environmental procedures

Why should lead-acid batteries be charged in a well-ventilated area?

  1. To improve the charging speed of the battery
  2. To prevent the battery from freezing in winter
  3. To disperse hydrogen gas during charging Correct answer.
  4. To keep the battery charger from overheating

Explanation

Lead-acid charging can produce hydrogen gas, which is flammable and can accumulate in a closed space. Good ventilation keeps the gas concentration low and reduces the risk of ignition.

Question 11Workshop safety, tools and environmental procedures

What should be used first to contain a small solvent spill?

  1. A stiff broom used dry
  2. A compressed air blow gun
  3. A water hose set to a fine spray
  4. Absorbent granules from the kit Correct answer.

Explanation

Absorbent granules or pads contain the liquid and stop it spreading toward drains or walkways. The used absorbent is then placed in a suitable container for hazardous waste disposal.

Question 12Workshop safety, tools and environmental procedures

Why is local exhaust ventilation used when spraying paint?

  1. To reduce the noise level of the workshop compressor
  2. To speed up the paint drying process in the booth
  3. To remove paint mist from the breathing zone Correct answer.
  4. To increase the pressure at the spray gun nozzle

Explanation

Local exhaust ventilation captures paint mist and solvent vapour near the source before they enter the technician's breathing zone. This reduces exposure to harmful airborne chemicals.

Question 13Workshop safety, tools and environmental procedures

Before repairing an electrically powered bench tool, what should be done?

  1. Remove the fuse and keep it in your pocket
  2. Leave the tool running on its lowest speed
  3. Ask a colleague to hold the power switch
  4. Isolate the power and lock it off Correct answer.

Explanation

The tool must be isolated from its energy source and locked off so that it cannot be re-energised while someone is working on it. A lock and tag also warn others that maintenance is in progress.

Question 14Workshop safety, tools and environmental procedures

What is the correct way to lift a heavy component from the floor?

  1. Bend at the waist and keep the legs straight
  2. Bend the knees and lift with the legs Correct answer.
  3. Twist the body while lifting to save time
  4. Hold the load out at arm's length

Explanation

Bending the knees and lifting with the leg muscles keeps the load closer to the body and reduces strain on the lower back. Twisting or holding the load away from the body increases the risk of injury.

Question 15Workshop safety, tools and environmental procedures

What should be done with a portable electrical tool that has a damaged power lead?

  1. Wrap the lead in insulating tape and use it
  2. Plug it into a longer extension lead
  3. Withdraw it and report the damage Correct answer.
  4. Use it only for low-power workshop jobs

Explanation

A damaged lead can expose live conductors and cause electric shock or fire. The tool should be taken out of service and reported so that it is repaired or replaced by a competent person.

Question 16Workshop safety, tools and environmental procedures

Which glove material is generally suitable for handling organic solvents?

  1. Cotton gloves worn under work gloves
  2. Disposable polyethylene gloves for quick tasks
  3. Leather gloves used for general handling
  4. Nitrile gloves rated for that chemical Correct answer.

Explanation

Glove resistance depends on the specific chemical, so the selected glove must be rated for the solvent being handled. Nitrile is common, but the chemical resistance chart must be checked before use.

Question 17Workshop safety, tools and environmental procedures

How should brake dust be cleaned from a wheel assembly?

  1. Use a damp cloth or HEPA vacuum Correct answer.
  2. Brush it dry so it disperses into the air
  3. Blow it off with a compressed air line
  4. Wash it into the workshop drain with water

Explanation

Brake dust can contain harmful particles, so it should be removed with a damp cloth or a vacuum fitted with a HEPA filter. Dry brushing or compressed air makes the dust airborne and increases inhalation risk.

Question 18Workshop safety, tools and environmental procedures

What is the correct disposal route for used engine coolant?

  1. Mix it with the used engine oil
  2. Put it in a labelled hazardous waste drum Correct answer.
  3. Dispose of it with general workshop waste
  4. Pour it down a storm drain outside

Explanation

Used coolant contains chemicals that are harmful to the environment and must be collected as hazardous waste. Keeping it in a labelled drum prevents mixing and allows authorised disposal.

Question 19Workshop safety, tools and environmental procedures

Why should water be drained from an air compressor receiver regularly?

  1. To increase the oil level in the pump
  2. To raise the output pressure of the compressor
  3. To lubricate the air tools automatically
  4. To prevent corrosion and water in tools Correct answer.

Explanation

Condensed water collects in the receiver and can corrode the tank or travel into air tools and paint lines. Draining it regularly keeps the compressed air supply dry and protects the equipment.

Question 20Workshop safety, tools and environmental procedures

What is the main hazard of using a hydraulic press without a correctly placed support or guard?

  1. The press automatically reverses its travel
  2. The workpiece becomes strongly magnetized
  3. The hydraulic oil becomes flammable at room temperature
  4. The workpiece can eject or the frame can fail Correct answer.

Explanation

A press stores large forces, and an unstable workpiece can be thrown out or the press structure can be overloaded. Correct support, guards, and rated tooling keep the load controlled.

Question 21Workshop safety, tools and environmental procedures

When servicing an air-conditioning system, why must refrigerant be recovered rather than vented?

  1. To increase the system operating pressure
  2. To protect the environment and follow the law Correct answer.
  3. To avoid using a vacuum pump
  4. To improve the vehicle's fuel economy on the road

Explanation

Refrigerant released to the atmosphere can contribute to climate change and is controlled by environmental regulations. Recovery equipment captures it for recycling or proper disposal.

Question 22Workshop safety, tools and environmental procedures

Before working on a fuel tank, what is a critical safety precaution?

  1. Purge the tank and control sparks Correct answer.
  2. Work alone so you are not distracted
  3. Use an open flame to check for leaks
  4. Fill the fuel tank completely to the top

Explanation

Fuel tanks can contain flammable vapour even when they appear empty, so the tank must be emptied and purged and ignition sources must be controlled. Working alone is unsafe for this type of task.

Question 23Workshop safety, tools and environmental procedures

After finishing hot work such as welding or grinding, what should be done?

  1. Turn off the workshop lights and lock up
  2. Leave the area immediately after finishing
  3. Open all solvent containers to air them
  4. Keep a fire watch for smoldering material Correct answer.

Explanation

Hot work can leave sparks or hot material that smolder for some time after the flame or spark source is removed. A fire watch checks the area and helps ensure that a fire does not start unnoticed.

Question 24Workshop safety, tools and environmental procedures

If a chemical splashes into a technician's eye, what is the first action?

  1. Rinse at an eyewash for 15 minutes Correct answer.
  2. Rub the eye firmly with a clean cloth
  3. Apply neutralising chemicals directly to the eye
  4. Wait to see whether irritation develops

Explanation

Immediate flushing at an eyewash station is the priority because it dilutes and removes the chemical from the eye. Flushing should continue for at least 15 minutes while medical help is arranged.

Question 25Workshop safety, tools and environmental procedures

Which class of fire extinguisher is appropriate for a fire involving petrol or paint thinner in a workshop?

  1. Class D, for combustible metals such as magnesium
  2. Class B, for flammable liquids such as petrol and solvents Correct answer.
  3. Class A, for solid combustibles such as wood and paper
  4. Class C, for flammable gases such as propane

Explanation

Flammable liquids burn as Class B fires and are tackled with foam, dry powder or carbon dioxide rather than water, which can spread the burning liquid. Petrol, thinners and similar solvents therefore call for an extinguisher carrying a Class B rating.

Question 26Workshop safety, tools and environmental procedures

Why should a file never be used without a securely fitted handle?

  1. Without a handle the file cuts more slowly and needs more force
  2. The teeth clog faster when the file is used without a handle
  3. The file loses its temper from the heat of a bare hand
  4. The sharp tang can pierce the user's hand if the file jams Correct answer.

Explanation

A file tang is a sharp spike intended to be driven into a wooden or plastic handle. If the file is used bare, a sudden jam or slip drives that spike into the palm or wrist, producing a deep puncture wound, so a sound handle is mandatory.

Question 27Workshop safety, tools and environmental procedures

How should rags soaked with oil or solvent be dealt with immediately after use?

  1. Stored in an open plastic bag until the weekly collection
  2. Tossed into the general waste bin at the end of the shift
  3. Spread out to dry on the bench so the solvent can evaporate
  4. Placed straight into a lidded metal bin for oily waste Correct answer.

Explanation

Oily and solvent-soaked rags generate heat as they oxidise and can self-ignite, particularly when bunched together. A lidded metal container limits oxygen and vapour, and the contents must be emptied or collected on a regular schedule.

Question 28Workshop safety, tools and environmental procedures

Two technicians are servicing the same machine. Technician A has already fitted a lock and tag on the isolator. What should technician B do before starting work?

  1. Remove A's tag and replace it with one in B's name
  2. Work under A's lock, because A is on site for the whole job
  3. Fit a personal lock to the same isolation point Correct answer.
  4. Ask a supervisor to hold the key to A's lock during the work

Explanation

Every person exposed to the machine must attach their own lock and tag to the isolation device, so the supply cannot be restored while anyone is still working. A's lock protects A alone, whereas B's own lock stays in place until B is clear.

Question 29Workshop safety, tools and environmental procedures

What is the main purpose of keeping solvents in a purpose-built flammable liquids cabinet?

  1. To allow unlabelled containers to be stored together
  2. To prevent any vapour from escaping into the workshop air
  3. To keep the solvent permanently below its flash point in hot weather
  4. To contain spills and delay flames reaching the contents Correct answer.

Explanation

A flammable liquids cabinet has a sump to hold leakage and fire-resisting walls that delay flames reaching the containers, giving people time to escape and the fire service time to respond. It also separates vapours from ignition sources, but it cannot change the liquid's physical properties.

Question 30Workshop safety, tools and environmental procedures

How should a compressed gas cylinder be kept when it is not connected for use?

  1. Lying flat on the floor with the regulator still attached
  2. Upright, secured by a chain or strap, with the valve cap fitted Correct answer.
  3. Chained upright with the regulator left on and the valve open
  4. Standing loose in a corner so it can be moved quickly

Explanation

Cylinders are stored upright and restrained so they cannot fall and shear the valve, and the protection cap is refitted whenever the regulator is removed. A sheared valve can turn a cylinder into a projectile, which is why loose or horizontal storage is unacceptable.

Question 31Workshop safety, tools and environmental procedures

A vehicle has been raised with a trolley jack so that work can be done underneath. What must be in place before anyone goes under it?

  1. The road wheels removed to give more working room
  2. A second trolley jack placed under the sill as a backup
  3. Axle stands placed under the vehicle at the correct support points Correct answer.
  4. The jack handle tied down so the release valve cannot move

Explanation

A hydraulic jack can bleed down or lose pressure, so the raised vehicle must rest on rated axle stands positioned at the manufacturer's lifting points before anyone works beneath it. The jack is a lifting device only and is never used as a support.

Question 32Workshop safety, tools and environmental procedures

What does the flash point of a solvent tell a technician?

  1. The temperature at which the liquid ignites without any spark
  2. The temperature at which burning vapour stops being produced
  3. The lowest temperature at which it gives off ignitable vapour Correct answer.
  4. The highest temperature at which the liquid may safely be stored

Explanation

Flash point is the lowest temperature at which a liquid releases enough vapour to form a flammable mixture with air at its surface. A low flash point means the liquid is a serious fire risk at normal workshop temperatures, which governs how it is stored, dispensed and ventilated.

Question 33Workshop safety, tools and environmental procedures

Repeated hand injuries occur at a press. Which measure is preferred under the hierarchy of controls?

  1. Fitting an interlocked guard over the danger zone Correct answer.
  2. Issuing cut-resistant gloves and training operators to wear them
  3. Displaying warning signs and adding the hazard to induction
  4. Shortening shifts so operators are less tired

Explanation

The hierarchy ranks controls by how reliably they remove risk: elimination, substitution, engineering controls, administrative controls, then PPE. An interlocked guard is an engineering control that physically prevents access to the hazard for everyone, whereas signs, training, shift patterns and gloves all depend on human behaviour.

Question 34Workshop safety, tools and environmental procedures

A workshop stores a 200-litre drum plus several 25-litre cans of solvent. How should the secondary containment be sized?

  1. Large enough to hold the full contents of every container stored
  2. At least 110% of the largest container, and around 25% of the total where volumes are large Correct answer.
  3. Equal to the combined contents of the smaller cans only
  4. Deep enough to cover the base of each container standing in it

Explanation

Secondary containment is normally sized to hold at least 110% of the largest container, so failure of that single drum is fully captured. Where the total inventory is large, the bund may also need to hold roughly 25% of the total stored volume, whichever figure is the greater.

Question 35Engine and driveline systems

In a four-stroke spark-ignition engine, which sequence lists the strokes in the correct order?

  1. Compression, intake, power, exhaust
  2. Intake, power, compression, exhaust
  3. Intake, compression, power, exhaust Correct answer.
  4. Power, intake, compression, exhaust

Explanation

A four-stroke cycle runs intake, compression, power and exhaust in that order, with the crankshaft turning twice per complete cycle. The intake stroke draws the charge in, compression raises its pressure, the power stroke follows combustion, and exhaust clears the cylinder for the next cycle.

Question 36Engine and driveline systems

How is the compression ratio of a reciprocating engine defined?

  1. The ratio of intake manifold pressure to exhaust manifold pressure
  2. The ratio of cylinder bore diameter to piston stroke length
  3. The ratio of swept volume to clearance volume
  4. The ratio of total cylinder volume at bottom dead centre to clearance volume at top dead centre Correct answer.

Explanation

Compression ratio is the cylinder volume at bottom dead centre divided by the clearance volume at top dead centre, which equals (swept volume plus clearance volume) divided by clearance volume. It sets how far the charge is compressed and therefore how much expansion is available on the power stroke, with knock limiting how high it can go on a given fuel.

Question 37Engine and driveline systems

In a conventional diesel engine, how is the air-fuel mixture ignited?

  1. By a glow plug that stays energised throughout running
  2. By a spark plug fired by the ignition coil
  3. By a pilot flame from a small pre-chamber spark plug
  4. By the heat of compression raising the air above the fuel ignition point Correct answer.

Explanation

A diesel draws in air only and compresses it to a high ratio, so its temperature rises above the fuel self-ignition point. Fuel injected near top dead centre then ignites spontaneously, with no external ignition source in normal running.

Question 38Engine and driveline systems

Why must a mechanical valvetrain have a specified clearance between the rocker and the valve stem?

  1. To keep the valve spring from binding at full lift
  2. To increase valve lift at high engine speed
  3. To ensure the valve still closes fully when the head and stem expand with heat Correct answer.
  4. To allow oil to reach the valve guide

Explanation

Metal parts grow as the engine reaches operating temperature, so a small gap is left to absorb that expansion. Without it the valve would be held slightly off its seat when hot, causing compression loss, burnt seats and rough running.

Question 39Engine and driveline systems

What energy source drives the turbine of a turbocharger?

  1. The intake air rushing into the cylinders
  2. An electric motor powered by the alternator
  3. A belt drive taken from the crankshaft pulley
  4. The pressure and heat of the exhaust gas leaving the engine Correct answer.

Explanation

Exhaust gas expands through the turbine wheel, and the turbine drives the compressor on the same shaft. This recovers energy that would otherwise be wasted, which is what separates a turbocharger from a mechanically driven supercharger.

Question 40Engine and driveline systems

What is the main purpose of an intercooler on a turbocharged engine?

  1. To warm the intake charge for better fuel vaporisation
  2. To cool the exhaust gas before it reaches the turbine
  3. To cool the compressed charge so it is denser and less prone to knock Correct answer.
  4. To cool the engine coolant before it returns to the radiator

Explanation

Compressing air raises its temperature, which lowers density and encourages detonation. The intercooler removes that heat so a greater mass of air fills the cylinder and the knock limit is pushed back, allowing more boost or more spark advance.

Question 41Engine and driveline systems

What does the coolant thermostat do in an engine cooling system?

  1. It opens and closes coolant flow to the radiator to hold the engine near its design temperature Correct answer.
  2. It switches the radiator fan on and off at set temperatures
  3. It limits the maximum pressure in the cooling system
  4. It circulates coolant through the block whenever the engine is running

Explanation

The thermostat is a temperature-controlled valve that stays closed during warm-up so coolant bypasses the radiator. It opens at its rated temperature to control flow through the radiator, keeping the engine in its efficient operating band.

Question 42Engine and driveline systems

In a multigrade oil marked 10W-30, what does the 10W indicate?

  1. The oil resistance to foaming under high-speed running
  2. The maximum ambient temperature at which the oil may be used
  3. The oil low-temperature viscosity behaviour, with W standing for winter Correct answer.
  4. The oil viscosity at 100 degrees Celsius in centistokes

Explanation

The number before the W is the winter or low-temperature grade, reflecting how easily the oil flows when cold. The number after the W is the high-temperature grade measured at around 100 degrees Celsius, so a lower W number means easier cold cranking.

Question 43Engine and driveline systems

In a torque converter, what produces the extra torque multiplication at low vehicle speed?

  1. The lock-up clutch clamping the turbine to the impeller
  2. The turbine blades reversing the direction of the fluid
  3. The stator redirecting fluid from the turbine back to the pump Correct answer.
  4. The overrunning clutch releasing the pump at high speed

Explanation

At low turbine speed the fluid leaves the turbine in a direction that would oppose the pump. The stator redirects it back to the pump in the direction of rotation, adding torque, and its one-way clutch lets it freewheel once the turbine approaches pump speed.

Question 44Engine and driveline systems

A vehicle engine speed rises sharply when the accelerator is pressed in third gear, but road speed climbs only slowly. Which fault fits this symptom?

  1. A worn clutch friction disc that cannot transmit full engine torque Correct answer.
  2. A seized front wheel bearing
  3. A blocked fuel filter restricting flow
  4. A dragging clutch release bearing

Explanation

If engine speed rises without a matching rise in road speed, the clutch is slipping because the friction disc cannot carry the torque. Wear, oil contamination or insufficient clamp load from a weak pressure plate are the usual reasons.

Question 45Engine and driveline systems

What is the job of a synchronizer ring in a manual gearbox?

  1. To pump lubricant to the gear bushes
  2. To hold the gear lever in the selected position
  3. To multiply the torque delivered to the output shaft in low gears
  4. To bring the gear and shaft to matching speed before the dog teeth engage Correct answer.

Explanation

The synchronizer uses cone friction to drag the engaging parts to the same speed before the dog teeth mesh. This prevents gear clash and allows smooth shifts without double-clutching.

Question 46Engine and driveline systems

What does the differential in a rear-wheel-drive axle do?

  1. It applies the final drive torque multiplication to the propeller shaft
  2. It disconnects drive to the wheels when the handbrake is applied
  3. It splits drive to the two wheels while allowing them to rotate at different speeds in a turn Correct answer.
  4. It locks both wheels together so they always turn at the same speed

Explanation

In a corner the outer wheel travels a longer path than the inner wheel, so the differential lets them rotate at different speeds while still dividing torque between them. A standard open differential divides torque roughly equally, limited by the wheel with less grip.

Question 47Engine and driveline systems

A vehicle is re-geared from a 3.08 to a 4.10 final drive ratio with no other changes. What is the likely effect?

  1. No change in acceleration, only in the speedometer reading
  2. Better acceleration and a lower top speed at the same engine speed Correct answer.
  3. Slower acceleration and a lower top speed
  4. Better acceleration and a higher top speed

Explanation

A numerically higher final drive gives more wheel torque for the same engine output, so acceleration improves. The trade-off is that the engine reaches its speed limit at a lower road speed, so top speed falls unless the engine can pull beyond its previous limit.

Question 48Engine and driveline systems

Why are constant-velocity joints used on the driveshafts of a front-wheel-drive car?

  1. They carry drive smoothly through large steering angles at constant speed Correct answer.
  2. They let the shaft change length without a sliding spline
  3. They multiply the torque delivered to the wheel by a fixed ratio
  4. They let the wheel freewheel when engine drive is removed

Explanation

A front driveshaft must work through large steering and suspension angles, and a simple universal joint would make the output speed fluctuate each revolution. Constant-velocity joints keep the driven shaft speed steady at those angles, avoiding vibration and roughness.

Question 49Engine and driveline systems

What does the engine management system do when the knock sensor detects detonation?

  1. It retards ignition timing to reduce cylinder pressure and stop the knock Correct answer.
  2. It switches off the injectors for the affected cylinder
  3. It advances ignition timing to burn the fuel sooner
  4. It enriches the mixture permanently to cool the charge

Explanation

Detonation is uncontrolled end-gas ignition that can damage pistons and bearings. The control unit responds by retarding timing, and on turbocharged engines often by reducing boost, until the knock signal disappears.

Question 50Engine and driveline systems

What is the function of the positive crankcase ventilation system?

  1. It seals the crankcase so that no gas can leave it
  2. It adds oil mist to the intake charge to lubricate the valves
  3. It vents crankcase pressure to atmosphere through a filter
  4. It routes crankcase blow-by gases into the intake to be burned, controlled by the PCV valve Correct answer.

Explanation

Blow-by past the rings pressurises the crankcase with gases containing unburned hydrocarbons. The PCV valve meters these gases into the intake so they are burned, and the system keeps the crankcase slightly below atmospheric so seals do not leak.