Explanation

World Wetlands Day is celebrated every year on 2nd February, marking the date of adoption of the Ramsar Convention on Wetlands in 1971 at Ramsar, Iran. India is a party to the Convention and uses the day to promote wetland conservation (India now has 80+ Ramsar sites). The other dates — 10th June, 13th February, 9th March — have no such association. Hence option D.