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
About Pneumocystis pneumonia the true statement is: 
Select and explain. 
A. The causative organism is a protozoan, B. Drug of choice is Trimethoprim-Sulfamethoxazole (Cotrimoxazole), C. Most common radiological appearance is a bat wing distribution of infiltrates with pneumocysts in peripheral fields, D. Steroids have no role in the therapy of Pneumocystis pneumonia
B: Drug of choice is Trimethoprim-Sulfamethoxazole (Cotrimoxazole)
Answer: B: Drug of choice is Trimethoprim-Sulfamethoxazole (Cotrimoxazole) 
Explanation: Pneumocystis jirovecii is a fungus responding to Cotrimoxazole. It causes opportunistic pneumonia in patients with HIV infection. 
The most common radiology finding is a normal X-ray chest.  However, the most typical X-ray is  a bat wing distribution of infiltrates with pneumocysts in peripheral fields. 
Steroids are combined with Cotrimoxazole in treatment of severe Pneumocystis jirovecii pneumonia.