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': 'Major signs included by WHO for AIDS diagnosis - \nSelect and explain. \nA. Chronic diarrhea > 1 month, B. Chronic cough > 1 month, C. Chronic fever > 1, D. Weight loss of at least 10% of body weight', 'role': 'user'}, {'content': "Answer: A \nExplanation: The initial evaluation of a patient with HIV infection and diarrhea should include a set of stool examinations, including culture, examination for ova and parasites, and examination for Clostridium difficile toxin.In patients for whom this diagnostic evaluation is nonrevealing, a presumptive diagnosis of HIV enteropathy can be made if the diarrhea has persisted for >1 month. (Harrison's Principles of internal medicine, 20th edition, page 1511 )", 'role': 'assistant'}]