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: Pharmacology
[{'content': 'Terlipressin can be used for hematemesis from oesophageal varices. The action is mediated by: \nSelect and explain. \nA. V1a, B. V1b, C. V2, D. V4', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Terlipressin causes vasoconstriction by acting on V1a/V1\xa0receptor.\n(V1b\xa0receptor is also called as V3\xa0receptor)', 'role': 'assistant'}]