Explanation:

- The National Scheduled Tribes Commission was part of a larger shift to ensure the rights and welfare of the Scheduled Tribes in India.

- Initially, both Scheduled Castes and Scheduled Tribes were handled by a combined commission.

- Option 1: 2000 - Not correct. That's not when it came into its own.

- Option 2: 2006 - Incorrect year for the establishment of the separate commission.

- Option 3: 2004 - Correct Answer. The Commission for Scheduled Tribes became separate from the combined commission in 2004.

- Option 4: 2002 - Incorrect. Two years too early for the separate commission.