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: Surgery
A patient had undergone a renal transplantation 2 months back and now presented with difficulty breathing. X-ray showed bilateral diffuse interstial pneumonia. The probable etiologic agent would be ? 
Select and explain. 
A. CMV, B. Histoplasma, C. Candida, D. Pneumocystic carinii
A: CMV
Answer: A: CMV 
Explanation: Ans is 'a' i.e. CMV CMV is the most common oppounistic infection in a renal transplant (or any organ transplant) patient. It does not generally appear until the end of the first post-transplant month. Infection in the first post-transplant month are most commonly due to conventional nosocomial infections.