Reconstruct a geological sequence from stated relationships

In this fictional field exercise, a simplified cross-section contains three sedimentary units labeled A, B and C. The field description states that A was deposited first, B overlies A, and C overlies B,with no overturned beds. All three units were subsequently folded. A granitic intrusion D cuts the folded beds and contains fragments of B. An erosional surface truncates both the folded strata and the top of D. A horizontal sandstone E rests on that surface and is not cut by the intrusion. No fault is shown and no numerical age has been measured. The diagram is deliberately simplified so that the task concerns relative relationships rather than a named real locality. A classmate proposes that D must be younger than E because granite is always the youngest rock type. Another proposes an exact age for the folding from the color of the sandstone. You must evaluate those proposals using only the stated evidence.