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: Pathology
[{'content': 'PNH occurs due to defect in: \nSelect and explain. \nA. CD 59, B. CD 15, C. CD 100, D. CD 20', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]