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
Hereditary angioneurotic edema is due to ? 
Select and explain. 
A. Deficiency of C1 inhibitor, B. Deficiency of NADPH oxidase, C. Deficiency of MPO, D. Deficiency of properdin
A: Deficiency of C1 inhibitor
Answer: A: Deficiency of C1 inhibitor 
Explanation: Ans. is 'a' i.e., Deficiency of C1 inhibitor Hereditary angioneurotic edema is due to C1inhibitor (Ci esterase inhibitor) deficiency.