This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': 'Maximum tolerable limit for heat is - \nSelect and explain. \nA. 30 HSI, B. 50 HSI, C. 80 HSI, D. 100 HSI', 'role': 'user'}, {'content': "Answer: D \nExplanation: Park's textbook of preventive and social medicine 23rd edition. *Heat stress index values - no thermal stress -30. _ moderate to mild heat strain -60 _ severe heat strain -90 _ very severe heat strain _ upper limit of heat tolerance.", 'role': 'assistant'}]