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 a slack of two days.

E) F is critical, and has zero slack.

Group of answer choices

D

E

B

A

C