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: Microbiology
Cholera vaccine effectiveness is - 
Select and explain. 
A. 20% for 12 months, B. 50% for 12 months, C. 20% for 36 months, D. 50% for 36 months
B: 50% for 12 months
Answer: B: 50% for 12 months 
Explanation: Ans. is 'b' i.e., 50% for 12 months