Which of the following states is included in the sixth schedule of the Constitution of India?

Mizoram

The correct answer is Option 3 - Mizoram

Out of the listed states, only Mizoram is included in the Sixth Schedule of the Constitution of India.

Sixth Schedule: This schedule provides special provisions for the administration of tribal areas in specific states.
States covered: Assam, Meghalaya, Tripura, and Mizoram.
While Nagaland, Manipur, and Arunachal Pradesh have significant tribal populations, they are not covered under the Sixth Schedule. Some of these states might have their own tribal area administration provisions, but they wouldn't be under the central Sixth Schedule.