This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Location of a-1 sympathetic receptors? \nSelect and explain. \nA. Blood vessels, B. Bronchi, C. Sweat glands, D. Hea', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is'a' i.e., Blood vessels(Ref: Ganong 25thie p. 260)", 'role': 'assistant'}]