Which process requires an estimation of the work effort and available resources to complete an activity?

The process that involves estimating the work effort and available resources to complete an activity is the one focused on estimating activity durations. This process is crucial because it aims to determine how long each activity in the project is expected to take, which inherently requires insights into both the effort involved and the resources that will be applied.

During the estimation of activity durations, project managers typically consider various factors such as the complexity of the tasks, team capabilities, historical data, and available resources. This not only helps in creating a realistic project schedule but also ensures that the team can allocate appropriate resources effectively. Accurate duration estimation is foundational for successful project planning, as it influences the overall project timeline and resource management.

In contrast, defining activities is more about identifying and documenting the specific tasks required to achieve the project's objectives without delving into resource allocation or effort estimation. Planning resource management involves determining how the project resources will be estimated, acquired, and managed but does not specifically focus on estimating the duration of activities. Control resources, on the other hand, deals with monitoring and adjusting resource use throughout the project, again not directly tied to the initial estimation of work effort and duration for activities.