Final answer:
The nursing intervention for a client undergoing a posterior iliac crest bone marrow aspiration is to place the client in a prone position, remain in the prone position for a few hours after the procedure, and apply pressure to the site for 5 minutes to prevent bleeding.
Step-by-step explanation:
The nursing intervention for a client undergoing a posterior iliac crest bone marrow aspiration is to place the client in a prone position (option a). This position allows for easy access to the iliac crest area. The client should remain in the prone position for a few hours after the procedure to prevent bleeding (option b). It is important to apply pressure to the site for 5 minutes (option d) to help prevent bleeding.