You are answering a USMLE-style medical question. Question: A 72-year-old woman is brought to the physician by her daughter because of a 6-month history of worsening short-term memory deficits and social withdrawal. Treatment with galantamine is initiated. Two weeks later, the patient develops vomiting, mild crampy abdominal pain, and watery, nonbloody diarrhea. Which of the following is the most appropriate pharmacotherapy? Options: A) Bethanechol B) Metoclopramide C) Atropine D) Oxybutynin Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.