The correct answer is D. All of the above.
In critical path method (CPM) network analysis of projects, the earliest start time (EST) of an activity is the earliest time at which the activity can start, given the start times of the activities that must precede it. The latest start time (LST) of an activity is the latest time at which the activity can start without delaying the project. The latest finish time (LFT) of an activity is the latest time at which the activity can finish without delaying the project. The duration of an activity is the amount of time it takes to complete the activity.
The EST of an activity is equal to the earliest finish time of the activity that must precede it, plus the duration of the activity. The LST of an activity is equal to the latest finish time of the project, minus the duration of the activity.
The critical path is the path through the network that takes the longest time to complete. The critical activities are the activities on the critical path. The critical path and critical activities determine the earliest possible completion time for the project.
If an activity on the critical path is delayed, the entire project will be delayed. If an activity that is not on the critical path is delayed, the project will not be delayed, but the earliest possible completion time for the project may be delayed.
CPM network analysis is a powerful tool for planning and scheduling projects. It can help to ensure that projects are completed on time and within budget.