You are answering a USMLE-style medical question. Question: The parents of a 16-year-old boy with type 1 diabetes mellitus present requesting information about the drug, exenatide, an injectable drug that only needs to be administered once a week. The patient’s blood glucose levels have been difficult to control on his current insulin regimen due to poor adherence to recommended therapy, and he has had difficulty putting on weight despite eating copiously. The patient is afebrile and his vital signs are within normal limits. His body mass index (BMI) is 19 kg/m2. Which of the following best describes why the patient should not be switched to exenatide? Options: A) Insulin production by the pancreas is insufficient for exenatide to be effective. B) Exenatide suppresses glucagon secretion, which increases the risk of hypoglycemia. C) Suppression of appetite makes it even harder for him to gain weight. D) Exenatide is contraindicated in children below 18 years. Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.