When was it was announced that Sikkim had become the first state in India to achieve 100% sanitation coverage attaining the status of "Nirmal State"?

The correct answer is Option D: 8^th December 2008.

Let's break down why:

Sanitation Coverage: This refers to having proper toilet facilities and waste disposal systems for everyone in the state.

"Nirmal State": This is a title given to states in India that have achieved 100% sanitation coverage.

The Date: It was officially announced on December 8, 2008, that Sikkim had reached this milestone, making it the first state in India to do so.