The correct answer is option 2, Sikkim. Sikkim is the least populated state in India. It is a small state located in the northeastern part of the country. Sikkim has a relatively low population compared to other states in India.
Option 1, Arunachal Pradesh, is not the least populated state. It is the largest state in northeastern India and has a higher population than Sikkim.
Option 3, Mizoram, is also not the least populated state. It is another northeastern state with a higher population than Sikkim.
Option 4, Uttarakhand, is not the least populated state either. It is a northern state in India and has a higher population than Sikkim.
Therefore, the correct answer is Sikkim, as it is the state with the lowest population in India.