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
Maximum tolerable limit for heat is - 
Select and explain. 
A. 30 HSI, B. 50 HSI, C. 80 HSI, D. 100 HSI
D: 100 HSI
Answer: D: 100 HSI 
Explanation: 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.