This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: GIT, Subject name: Surgery
[{'content': 'Serotonin (5-HT) is one of several mediators of the signs and symptoms of carcinoid tumor. When released from this neoplasm, most of the manifestations of 5-HT are the result of activation of the 5-HT2 receptor. These manifestations are therefore likely to include which of the following effects? \nSelect and explain. \nA. Bronchospasm, B. Constipation, C. Skeletal muscle weakness, D. Tachycardia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: - 5-HT2 receptors mediate smooth muscle contraction and thus cause bronchospasm and diarrhea, not constipation.- Skeletal muscle and cardiac muscle are relatively insensitive to 5-HT.- Peptic ulceration is not mediated in pa by 5-HT; the autacoid actually reduces acid secretion.', 'role': 'assistant'}]