What is the process of ensuring that project resources are assigned and available?

Control Resources monitors the actual versus planned use of resources and takes corrective action when variances occur - it does not initially acquire or assign resources to the project.

Acquire Resources is defined in the PMBOK Guide as the process of obtaining team members, facilities, equipment, materials, supplies, and other resources necessary to complete project work. This process formally assigns resources to the project and confirms their availability at the appropriate times, making it the direct answer for ensuring resources are assigned and available.

Control Resources (repeated choice) addresses monitoring and adjusting resource utilization after resources have already been acquired, not the initial process of making resources available.

Plan Procurement Management determines what to procure, how, and when - it produces procurement documents and strategies but does not directly result in resources being assigned and available.