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
Treatment of choice for pneumocystis carinii pneumonia is: 
Select and explain. 
A. Trimethoprim/sulfamethoxazole, B. Erythromycin, C. Ofloxacin, D. Tetracycline
A: Trimethoprim/sulfamethoxazole
Answer: A: Trimethoprim/sulfamethoxazole 
Explanation: None