The correct answer is D) maintain a uniform level of required resources.
The start of noncritical activities is delayed beyond their earliest start times (but not beyond their latest start times) in order to maintain a uniform level of required resources.
That is why companies have to establish their priorities and identify the main activities that must be accomplished on time, the people responsible to accomplish the activity, and the resources needed to successfully do so. Noncritical activities can be delayed up to a point, but the critical activities have to be followed according to the schedule.