Activity D on a CPM network has predecessors B and C,and has successor F.D has duration 6.B's earliest finish is 18,while C's is 20.F's late start is 26.Which of the following is definitely true?
A)B is a critical activity.
B)C is completed before B.
C)D has no slack but is not critical.
D)D is critical,and has zero slack.
E)F is critical,and has zero slack.

Question

Quizplus · Accepted Answer

Since activity D has predecessors B and C, its earliest start time will be the maximum of B's earliest finish time (18) and C's earliest finish time (20), which is 20. Therefore, D's earliest start time is 20, and with a duration of 6, its earliest finish time is 26.
Since F's late start time is also 26, activity F cannot start any later than its late start time without delaying the project. This means that activity D must finish before 26, making it a critical activity.
Furthermore, since activity D has no slack (i.e., the difference between its latest start time and earliest start time is zero), it must finish on its earliest finish time, which is 26. Therefore, D is critical and has zero slack.

Activity D on a CPM Network Has Predecessors B and C,and