The correct answer is: C. Crash durations for all the activities along the critical path obtained by taking into account the normal duration for all the activities.
The crash duration is the shortest possible time it takes to complete an activity. The critical path is the longest path through a project network diagram. The crash project duration is the shortest possible time it takes to complete a project. It is obtained by crashing the activities along the critical path. Crashing an activity means reducing its duration by increasing its cost.
Option A is incorrect because it does not take into account the critical path. Option B is incorrect because it does not take into account the normal duration of the activities. Option D is incorrect because it does not take into account the crash duration of the activities.