According to the PMBOK® Guide (6th Edition), Project Schedule Management includes the processes required to manage the timely completion of the project. There are six specific processes within this Knowledge Area:

Plan Schedule Management

Define Activities

Sequence Activities

Estimate Activity Durations

Develop Schedule

Control Schedule

Estimate Activity Durations is the process of estimating the number of work periods needed to complete individual activities with estimated resources. This process is critical for developing the overall project schedule.

Analysis of Distractors:

B (Create Work Breakdown Structure): This is a process within the Project Scope Management knowledge area. While the WBS provides the " framework " for the schedule, the act of creating it is fundamentally about defining the scope of work.

C (Direct and Manage Project Work): This is an executing process within the Project Integration Management knowledge area. It involves leading and performing the work defined in the project management plan.

D (Estimate Activity Resources): In the PMBOK® Guide 6th Edition, this process was moved to the Project Resource Management knowledge area. While resources heavily influence duration, the process itself is categorized under Resource Management because it focuses on the " what " and " who " rather than the " how long. "