When a Project Manager uses the crashing or fast tracking schedule compression technique, it is very important they consider which of the following: $($select the best possible answer$).$ A$.$ Crashing and fast tracking are schedule compression techniques that can create both opportunities and threats to the schedule.

B$.$ Crashing might add resources at additional cost to the project, but might not accomplish the desired result.

C$.$ Fast tracking might add time to the schedule due to the need for rework.

D$.$ All of the above.