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: Medicine
Pancytopenia is most common after: 
Select and explain. 
A. Hepatitis, B. Infective carditis, C. Pyelonephritis, D. Meningitis
A: Hepatitis
Answer: A: Hepatitis 
Explanation: Hepatitis is the most common preceding infection, and post hepatitis marrow failure accounts for about 5% of etiologies in most series. Patients are usually young men who have recovered from a bout of liver inflammation 1 to 2 months earlier; the subsequent pancytopenia is very severe. The hepatitis is seronegative (non-A, non-B, non-C, non-G) and possibly due to a novel, as yet undiscovered, virus. Ref: Harrison's principle of internal medicine 17th edition, chapter 102.