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
National switch day for polio vaccine is 
Select and explain. 
A. April 25, 2016, B. April 26, 2017, C. April 24, 2025, D. April 23, 2014
A: April 25, 2016
Answer: A: April 25, 2016 
Explanation: Change over from trivalent to bivalent oral polio vaccine vaccine is National switch day. It was on April 25, 2016.