The correct answer is: b) Assam
Meghalaya was a part of Assam prior to attaining statehood on 21st January 1972. It was a Union Territory from 1963 to 1972.
Option a) West Bengal is incorrect because Meghalaya is not a part of West Bengal.
Option c) Nagaland is incorrect because Meghalaya is not a part of Nagaland.
Option d) Manipur is incorrect because Meghalaya is not a part of Manipur.