Sikkim officially became the 22nd state of India in:

The correct answer is: b) 1975.

Sikkim officially became the 22nd state of India on May 16, 1975. Prior to that, it was an independent kingdom. In 1973, the Sikkim Agreement was signed between India and Sikkim, which paved the way for Sikkim’s merger with India. The agreement was ratified by the Indian Parliament in 1974 and by the Sikkim Assembly in 1975. On May 16, 1975, Sikkim became the 22nd state of India.

Option a) is incorrect because Sikkim did not become a state of India until 1975.

Option c) is incorrect because Sikkim did not become a state of India until 1975.

Option d) is incorrect because Sikkim did not become a state of India until 1975.