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: Microbiology
[{'content': 'Hereditary angioneurotic edema is due to deficiency of \nSelect and explain. \nA. C1 deficiency, B. C2 and C4 deficiency, C. C1 esterase inhibitor, D. C9 deficiency', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C1 esterase inhibitor causes Hereditary angioneurotic edema.', 'role': 'assistant'}]