Answer : 2. "24 October"
Explanation :

According to WHO, cases of polio virus have reduced by 99.9% since 1980. World Polio Day is celebrated every year on 24 October. On this day, awareness is spread to explain the importance of polio vaccination and in this fight to eradicate polio, support is given to those countries which are still struggling with polio. Polio has still not been completely eradicated. Therefore, necessary information related to polio must be obtained on this day.