The correct answer is b) 1949.
The princely state of Travancore and Kochi were integrated into the Indian Union on 1 July 1949. This was done through the Instrument of Accession, which was signed by the Maharaja of Travancore and the Maharaja of Kochi. The Instrument of Accession gave the Indian government control over the princely states, but it also allowed the princely states to retain some autonomy.
The integration of Travancore and Kochi into the Indian Union was a significant event in the history of India. It marked the end of the princely states in India and the beginning of a new era of unity and integration.
The other options are incorrect. Option a) 1947 is incorrect because India gained independence from British rule on 15 August 1947. Option c) 1956 is incorrect because the States Reorganisation Act, which integrated the princely states into the Indian Union, was passed in 1956. Option d) 1960 is incorrect because the formation of the state of Kerala, which was formed by the merger of Travancore and Cochin, took place in 1956.