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: Social & Preventive Medicine
[{'content': 'Maximum recommended number of students in a school class room \nSelect and explain. \nA. 30, B. 35, C. 40, D. 50', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]