In a PERT network, non$-$critical activities that have little slack need to be monitore closely:

A$)$ because near$-$critical paths could become critical paths with small delays in these activities.

B$)$ because they have a high risk of not being completed.

C$)$ because they are causing the entire project to be delayed.

D$)$ because slack is undesirable and needs to be eliminated.

E$)$ because PERT treats all activities as equally important.