Logical Reasoning: Argument Structure, Assumptions, and Answer-Choice Traps
Start with the conclusion
Every Logical Reasoning stimulus is either an argument or a set of facts waiting to become one. Find the conclusion first - the claim the author wants you to accept - then ask what the premises actually prove. The distance between what is stated and what is concluded is where the answer lives.
Concepts you must own
Conditional reasoning: from "if A then B" you may infer only the contrapositive (not B, therefore not A). Affirming the consequent and denying the antecedent are invalid. Quantifiers matter: "some" means at least one, "most" means more than half, and two "most" statements about the same group need not overlap. Causal conclusions require ruling out alternative causes, reverse causation, and coincidence. Statistical evidence must come from a representative sample, and claims about a group do not automatically transfer to an individual.
Recurring traps
Out-of-scope choices that are true but irrelevant; choices that are too strong ("all," "never") when the evidence supports only "some"; conditional reversals; answers that attack a premise instead of the reasoning; and answers that strengthen a little when the stem demands a sufficient assumption.
Rule of thumb
On Necessary Assumption questions, negate the choice. If the negation wrecks the argument, the choice is required. On Sufficient Assumption, ask whether adding the choice makes the conclusion airtight, even if the choice feels unnatural.
Worked example
"Reported burglaries fell 20 percent after streetlights were installed, so brighter streets deter burglars." A tempting answer says burglars dislike light, but the real gap is the reporting itself. "Residents began reporting burglaries to a new online portal only after the lights went in" weakens by supplying an alternative explanation for the drop.