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
[{'content': 'Reverse Cold Chain is used for - \nSelect and explain. \nA. Carrying stool samples of polio patiens from a PHC to the lab, B. Transpoing outdated vaccines from PHC to district hospital, C. Transpoing vaccines to lab.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', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 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.', 'role': 'assistant'}]