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': 'Number of holes per square inch of mosquito net is: \nSelect and explain. \nA. 100, B. 150, C. 250, D. 350', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 150', 'role': 'assistant'}]