The best answer is to track actual durations to measure the actual progress of the project. Actual duration is the time, in the calendar units, between the actual start date of the schedule activity and either the data date of the project schedule if the schedule activity is in development or the actual finish date if the schedule activity is complete.

Answer option B is incorrect. The schedule baseline is not created based on actual durations.

Answer option A is incorrect. Process improvement is part of the quality management knowledge area, but it is not a reason to track actual durations.

Answer option D is incorrect. Quality control is the inspection of the project deliverables. It is not concerned with the actual durations of project work. The improvement of the project processes is defined in the Process Improvement Plan.