Final answer:
The nurse should advise the client to avoid all oral intake to promote bowel rest during an acute exacerbation of ulcerative colitis.
Step-by-step explanation:
The physician has ordered bowel rest for the client with an acute exacerbation of ulcerative colitis. Bowel rest refers to reducing the activity of the bowel to allow it to heal. In this case, the nurse should advise the client to avoid all oral intake (option b). This means that the client should not consume any food or drink by mouth, including clear liquids, high-fiber foods, and caffeinated beverages.