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
Above which level of heat stress index it is not possible to work comfortably – 
Select and explain. 
A. 20 – 40, B. 40 – 60, C. 60 – 80, D. 80 – 100
B: 40 – 60
Answer: B: 40 – 60 
Explanation: HSI 40-60 causes severe heat strain and it is not possible to work comfortably.