Final answer:
The nurse would use a pressure-relieving mattress to care for the patient with a pressure ulcer on his back.
Step-by-step explanation:
For a patient with a pressure ulcer on his back, the nurse would perform the nursing intervention of using a pressure-relieving mattress (Option D). A pressure-relieving mattress helps distribute the patient's weight more evenly, reducing the pressure on the ulcer and promoting blood flow to the area. This can help prevent further damage to the tissues and promote healing.