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
Reverse Cold Chain is used for - 
Select and explain. 
A. Carrying stool samples of polio patiens from a PHC to the lab, B. Transpoing outdated vaccines from PHC to district hospital, C. Transpoing vaccines to lab. to check its potency, D. Transpoing vaccine form camps to sub - centre
A: Carrying stool samples of polio patiens from a PHC to the lab
Answer: A: Carrying stool samples of polio patiens from a PHC to the lab 
Explanation: Ans. is 'a' i.e., Carrying stool samples of polio patients from MC to lab "Reverse cold chain" is for transpo of ble poliovirus in stool to an investigation centre.