National Science Day is observed on February 28th every year in India. The correct answer is:

(B) February 28

National Science Day is celebrated to commemorate the discovery of the Raman Effect by Sir C.V. Raman on February 28, 1928. This day is dedicated to promoting the importance of science in daily life and encouraging scientific activities and research in the country. It is an occasion to acknowledge the contributions of scientists and highlight the significance of science and technology in various fields. The theme for National Science Day is chosen each year to focus on specific areas of scientific development and awareness.