Arunachal Pradesh achieved full statehood within the Indian Union in the year:

The correct answer is: c) 1987.

Arunachal Pradesh achieved full statehood within the Indian Union on February 20, 1987. It was previously a union territory.

Option a) is incorrect because Arunachal Pradesh was not a part of India in 1950. It was a part of the British Empire until 1947, when it became a part of the Dominion of India.

Option b) is incorrect because Arunachal Pradesh was not a part of India in 1972. It was still a union territory.

Option d) is incorrect because Arunachal Pradesh was not a part of India in 2000. It had already achieved statehood in 1987.