This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
[{'content': 'Which one is true about serotonin? \nSelect and explain. \nA. Sleep suppressant, B. Increase appitite, C. Vasoconstriction, D. Bronchodialtion', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Serotonin is a powerful vasoconstrictor, produces hyperpnea, increases tone of smooth muscle of intestine, bronchioles.(Ref: Textbook of physiology N Geetha 2nd edition page no.446)', 'role': 'assistant'}]