Which aspect of a project does the critical path primarily affect?

The critical path primarily affects the timeline for project completion. This is because the critical path consists of a sequence of project activities that determine the shortest time in which the project can be completed. Any delay in the activities on the critical path directly impacts the overall project schedule, leading to potential project delays.

Understanding the critical path allows project managers to prioritize tasks that are essential for on-time delivery and to manage resources accordingly. Hence, managing the critical path is vital for ensuring that the project adheres to its scheduled timeline and milestones, making choice C the most accurate answer in this context.