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
What is the most common opportunistic infection in AIDS? 
Select and explain. 
A. Tuberculosis, B. Cryptococcosis, C. Pneumocystitis carinii, D. Histoplasmosis
A: Tuberculosis
Answer: A: Tuberculosis 
Explanation: None