The main difference between PERT and CPM is that: A. PERT is more accurate than CPM. B. PERT assumes that activity durations are known. C. CPM assumes activity durations can vary. D. PERT employs three time estimates for each activity. E. PERT ignores activity costs.

PERT employs three estimates for each activity.

Explanation:

The Critical Path Method(CPM) and the Program Evaluation and Review Technique(PERT) are project management tools which are used to schedule and plan the activities in a project. CPM identifies the critical path which is gotten by calculating the longest path.

Program Evaluation and Review Method (PERT) is used when the prediction of the time each event takes is not known.

The critical path method uses a single time estimate whereas the PERT uses three time estimates which are optimistic, pessimistic and most likely estimate.