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
OKA strain is used to produce vaccine for ? 
Select and explain. 
A. Mumps, B. Measles, C. Japanese encephalitis, D. Chickenpox
D: Chickenpox
Answer: D: Chickenpox 
Explanation: Ans. is 'd' i.e., Chickenpox