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
Drug of choice for pneumocystis carinii is: 
Select and explain. 
A. Doxycycline, B. Cotrimoxazole, C. Tetracycline, D. Dapsone
B: Cotrimoxazole
Answer: B: Cotrimoxazole 
Explanation: Answer is B (Cotrimoxazole): Trimethoprim/sulfamethoxazole or Cotrimoxazole is the drug of choice for all firms of Pneumocystis Pneumonias. 'Trimethoprim-Sulfamethoxazole which acts by inhibiting folic acid synthesis is considered the drug of choice for all forms of Pneumocystis Pneumonias. Therapy is continued for 14 days in Non-HIV-Infected patients and for 21 days in HIV-Infected patients' - Harrison 18th/1672