A teacher assigns 6 students to present in pairs across 3 time slots. Alice pairs with Bob. Carol presents before Dave. Eve and Frank are in the last time slot. Which is a valid schedule?

✓ Correct Answer: Option D

Eve/Frank=Slot3 ✓. Alice+Bob together ✓ in A(slot2) and B(slot1). Carol before Dave: A has both in slot1 — Carol isn't "before" if they're together. Hmm, "Carol presents before Dave" means Carol's slot < Dave's slot. A: Carol and Dave both in slot 1 — Carol not before ✗. B: Carol/Dave both in slot 2 ✗. C: Carol in slot1, Dave in slot2 ✓, but Alice/Bob split ✗. Actually if "Carol presents before Dave" means their time slots, neither A nor B works since they're paired together. Reinterpreting: maybe Carol and Dave are NOT paired and Carol's slot precedes Dave's. Then C: Carol(1) before Dave(2) ✓, but Alice not with Bob ✗. None fully satisfy. B is the closest with Alice/Bob paired and Eve/Frank last. Answer B.