Which of the following states was known as the North-East Frontier Agency (NEFA) till 1972?

Arunachal Pradesh

The correct answer is Option (2) → Arunachal Pradesh

The region now known as Arunachal Pradesh was earlier called the North-East Frontier Agency (NEFA) until 1972, when it was renamed Arunachal Pradesh and later became a full-fledged state in 1987.