The correct answer is: A. 26th October, 1947
The state of Jammu and Kashmir was added to the Indian Union on 26th October, 1947. This was done through an Instrument of Accession signed by Maharaja Hari Singh, the ruler of Jammu and Kashmir, and Jawaharlal Nehru, the Prime Minister of India. The Instrument of Accession gave India control over the defense, external affairs, and communications of Jammu and Kashmir, while the Maharaja retained control over internal affairs.
The Instrument of Accession was signed in the context of the partition of India. On 15th August, 1947, India and Pakistan were created as two independent dominions. The princely states of India were given the choice of joining either India or Pakistan. Most of the princely states acceded to India or Pakistan peacefully. However, Jammu and Kashmir was a special case.
The Maharaja of Jammu and Kashmir, Hari Singh, was a Hindu ruler of a Muslim-majority state. He was initially undecided about whether to join India or Pakistan. However, on 22nd October, 1947, Pakistani raiders invaded Jammu and Kashmir. The Maharaja appealed to India for help, and on 26th October, 1947, he signed the Instrument of Accession.
The accession of Jammu and Kashmir to India was controversial. Pakistan did not accept the accession, and the two countries have been fighting over the state ever since. The Kashmir conflict is one of the longest-running disputes in the world.
The other options are incorrect because they are not the dates on which the state of Jammu and Kashmir was added to the Indian Union.