Final answer:
During the Planning Phase of a special project, a project manager asks how adding resources will affect the project's completion date.
Step-by-step explanation:
In the Planning Phase of a special project, a project manager asks the question, "How will adding resources now affect the project's completion date?" This is because the planning phase focuses on developing a detailed project schedule and determining the resources needed to complete the project. By considering the impact of adding resources at this stage, the project manager can assess how it may affect the project timeline and adjust accordingly.