Alan has more experience and knowledge in artificial intelligence methods and recent technologies. He is a critical resource, and multiple teams are looking for his assistance in their projects. Since he is busy with other activities on the critical path, then the critical path needs to add the dependency. It can change the critical path. Alan’s manager Tim is thinking about resource leveling. Resource leveling is used when?

A. Resources are in limited quantity.

B. Resource usage at constant level.

C. Resources are over-allocated and the necessary resources to do the task are available only on certain times.

D. All of the above.