When Sikkim becomes first state in India with 100 percent sanitation coverage?

The correct answer is C: 2008.

Here's why:

Sikkim achieved a significant milestone in environmental and public health by becoming the first state in India to achieve 100 percent sanitation coverage.
This means that every household in Sikkim had access to toilet facilities.
This accomplishment was reached in the year 2008.

The other options are incorrect because:

2006, 2007, and 2009 were not the years when Sikkim achieved 100% sanitation coverage.