The correct answer is (c). Tehri State merged with the Union of India in 1949.
Tehri State was a princely state in India that existed from the 11th century to 1949. It was located in the Garhwal Himalayas, in the present-day Indian state of Uttarakhand. The state was ruled by the Tehri Garhwal royal family, who were Rajputs.
In 1947, India gained independence from British rule. The princely states of India were given the choice of joining either India or Pakistan. Tehri State chose to join India. In 1949, Tehri State was merged with the Union of India and became a part of the United Provinces (now Uttar Pradesh).
The other options are incorrect. Option (a) is incorrect because Tehri State was not merged with the Union of India in 1920. Option (b) is incorrect because Tehri State was not merged with the Union of India in 1932. Option (d) is incorrect because Tehri State was not merged with the Union of India in 2000.