This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
[{'content': 'Most common cause of aplastic anemia is \nSelect and explain. \nA. Exposure to drugs, B. Viral hepatitis, C. Fanconi anemia, D. Fungal infection', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Aplastic anemia is pancytopenia with bone marrow hypocellularity. Acquired aplastic anemia is distinguished from iatrogenic aplasia, marrow hypocellularity after intensive cytotoxic chemotherapy for cancer, and from usually accidental physical and chemical injury, as in radiation poisoning. Most cases of aplastic anemia are idiopathic, little other than history separates these cases from those with a presumed etiology such as a drug exposure. ref - Harrisons internal medicine 20e pg 724', 'role': 'assistant'}]