World Wetland Day is a significant event celebrated globally to raise public awareness about the importance and value of wetlands. Each option offered a different date, but only one is correct.

Option 1 suggested 10th June, which is not the correct date for World Wetland Day.

Option 2 proposed 13th February, but this day marks `World Radio Day,` not World Wetland Day.

Option 3 gave 9th March, which again is inaccurate.

The correct date, as marked in Option 4, is 2nd February. This date was chosen because the Convention on Wetlands, known as the Ramsar Convention, was signed on 2nd February 1971 in the Iranian city of Ramsar. This international treaty aims to maintain the ecological character of wetlands and to plan for properly sustainable uses. Hence, 2nd February is celebrated as World Wetland Day every year.