A project manager is reviewing the project schedule and identifies that Task A (duration 5 days) must be completed before Task B (duration 3 days) can start. Task C (duration 4 days) can run in parallel with Task B. After Task B and C are complete, Task D (duration 6 days) can begin. What is the critical path duration for this sequence of tasks?

Correct answer: D. 14 days

Path 1: A -> B -> D = 5 + 3 + 6 = 14 days. Path 2: A -> C -> D = 5 + 4 + 6 = 15 days. Oh wait, Task C runs in parallel with B. So A (5 days) must complete. Then B (3 days) and C (4 days) can start. The parallel tasks B and C will take 4 days to complete (since C is longer). Then D (6 days) starts. So the critical path is A (5) + MAX(B (3), C (4)) + D (6) = 5 + 4 + 6 = 15 days. Let's re-read carefully: "Task C (duration 4 days) can run in parallel with Task B." This means B and C can both start after A. The path through B is 5 (A) + 3 (B) + 6 (D) = 14 days. The path through C is 5 (A) + 4 (C) + 6 (D) = 15 days. The critical path is the longest path, which is 15 days. My calculation with MAX was correct. The previous example explanation was wrong. The critical path is 15 days. Let's recheck options. No, it should be 15. The question might have a trick or my options are off. Let's assume the question means 'What is the minimum duration if these are the only tasks?' Then the critical path is the longest sequence. Path A-B-D: 5+3+6 = 14. Path A-C-D: 5+4+6 = 15. The critical path is 15 days. So the answer should be 15 days. Option C is 15 days. So the answer is C.