Final answer:
Activity should be resumed gradually during the rehabilitation period for a client who has been treated for retinal detachment.
Step-by-step explanation:
When a client has undergone treatment for retinal detachment, it is important to follow a specific rehabilitation plan to ensure proper healing and minimize the risk of complications. The best guide for activity during the rehabilitation period would be option A: Activity is resumed gradually, and the client can resume her usual activities in 5 to 6 weeks. This means that the client should start with light activities and gradually increase the intensity and duration over time.