Answer : 3. "28th फरवरी "
Explanation :

National Science Day in India is celebrated on February 28th every year. This day commemorates the discovery of the Raman Effect by the Indian physicist Sir C.V. Raman on February 28, 1928, for which he was awarded the Nobel Prize in Physics in 1930. National Science Day is an opportunity to recognize and celebrate the contributions of Indian scientists and to promote scientific temper and curiosity in the country.