When identifying an earlier project completion time, which is to be obtained by paying a premium for early completion, the activities that should be selected are those:

A. whose sum of activity time is the shortest.

B. that have zero slack time.

C. that give the longest possible completion time.

D. whose sum of slack time is the shortest.

Explanation:

A critical paths activity time is longer than that for any other path through the network. This path is important because if everything goes as scheduled, its length gives the shortest possible completion time for the overall project. Activities on the critical path become candidates for crashing, i.e., for reduction in their time by payment of a premium for early completion. Activities on the critical path have zero slack time and conversely, activities with zero slack time are on a critical path. By successively relaxing activities on a critical path, a curve showing total project costs vs. time can be obtained.