Manipur officially became a part of the Indian Union in:

The correct answer is: b) 1949.

Manipur officially became a part of the Indian Union on 15 October 1949, when the Instrument of Accession was signed between the Maharaja of Manipur, Bodhchandra Singh, and the Governor-General of India, Chakravarti Rajagopalachari. The Instrument of Accession was a document that allowed the princely states of India to join the Indian Union.

The other options are incorrect because:

• Option a) is the year India gained independence from British rule.
• Option c) is the year the States Reorganisation Act was passed, which reorganized the states of India.
• Option d) is the year Manipur became a full-fledged state of India.

I hope this helps! Let me know if you have any other questions.