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
Aplastic anemia results from 
Select and explain. 
A. Cytotoxic drugs, B. Whole body irradiation, C. HIV infection, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: None