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': 'Sling psychrometer is used for measuring ? \nSelect and explain. \nA. Air velocity, B. Rain fall, C. Median radiant temperature, D. Relative humidity', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e.. Relative humidity", 'role': 'assistant'}]