This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable Diseases, Subject name: Social & Preventive Medicine
Strain used for chickenpox vaccine: 
Select and explain. 
A. Edmonston Zagreb strain, B. Oka strain, C. 'Danish' 131, D. RA 27/3 strain
B: Oka strain
Answer: B: Oka strain 
Explanation: Ans. b (Oka strain). (Ref. Park PSM 22nd/pg. 137)VACCINESTRAIN USEDMeaslesHDC-Edmonston Zagreb strainBCG'Danish' 131Chicken pox (live attenuated)Oka strainOPVSabin strainIPVSalk strainRubellaRA 27/3 strain