Free PMI Project Management Professional Practice Question

The Early Start (ES) of an activity is determined by the latest Early Finish (EF) of its predecessors. In this case, Activity B has two predecessors: Activity A with an EF of 10, and Activity C with an EF of 15. Since we need to wait for both predecessors to finish before starting Activity B, we must use the later of the two EF values. Therefore, the ES for Activity B is 15, which is the EF of Activity C. This ensures that both predecessor activities have been completed before Activity B can begin.