CAPM Practice: Demonstrate an understanding of a project management plan schedule

An activity is the fundamental unit of work in a project schedule. It has a defined start, duration, resource requirements, and produces a specific output. Activities are derived from work packages in the WBS and are the units that are sequenced, estimated, and assigned in creating the project schedule.

**Why not A:** A milestone is a significant point or event in the project schedule, typically with zero duration. Unlike an activity, a milestone does not require resources or time to complete — it marks an achievement or checkpoint, not a unit of work.

**Why not B:** A high-level project deliverable is a product, result, or capability produced by the project. Deliverables are outputs of activities, not the activities themselves. An activity is the work performed to create deliverables, not the deliverable itself.

**Why not D:** A period reserved for risk management is not how activities are defined. While risk management activities can exist in a schedule, describing an activity generically as a time reservation for risk management mischaracterizes what a schedule activity represents.