Final answer:
Commands must keep enlisted performance evaluations for 5 years as they are critical for personnel decisions.
Step-by-step explanation:
Commands must retain copies of enlisted performance evaluations for the prescribed period of time. The correct answer to this question is C. 5 years. Performance evaluations are critical documents that are used for promotions, assignments, and other personnel decisions, hence their retention period is important for reference and record-keeping within the command structure.