This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infection, Subject name: Medicine
[{'content': 'Which of the following is zidovudine (AZT) a treatment for? \nSelect and explain. \nA. retroviral infection, B. pneumocystis carinii pneumonia, C. Kaposi sarcoma, D. toxoplasmosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: AZT is beneficial to patients with HIV infection, but the best time at which to commence therapy is still controversial. Common side effects include fatigue, macrocytic anemia, neutropenia, and myopathy. Treatment regimens now include protease inhibitors as well. Monotherapy with AZT results in development of resistance.', 'role': 'assistant'}]