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
Which of the following vaccine is MOST sensitive to heat? 
Select and explain. 
A. Measles, B. BCG, C. OPV, D. IPV
C: OPV
Answer: C: OPV 
Explanation: OPV is the most sensitive vaccine to heat requiring to be stored below -20 degree C. Measles vaccine also must be stored in the freezer compament. Ref: Park 21st edition, page 101.