The correct answer is (c) 1949.
Tehri State was a princely state in India that existed from 1815 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 1949, Tehri State merged with the Union of India. The merger was part of the process of Indian independence, and it was agreed upon by the Maharaja of Tehri Garhwal, Pratap Singh. The merger was a peaceful one, and it led to the creation of the new Indian state of Uttarakhand.
The other options are incorrect. Option (a), 1920, is incorrect because Tehri State was not a princely state in 1920. It was a part of the British Indian Empire. Option (b), 1932, is incorrect because Tehri State was still a princely state in 1932. Option (d), 2000, is incorrect because Tehri State was merged with the Union of India in 1949, not 2000.