The correct answer is C. 1940 AD.
Sirmaur Riyasati Praja Mandal was founded in 1940 AD by Thakur Amar Singh. It was a political party that fought for the rights of the people of Sirmaur. The party was successful in getting some of its demands met, such as the introduction of representative government in Sirmaur.
The other options are incorrect. Option A is incorrect because Sirmaur Riyasati Praja Mandal was founded in 1940 AD, not 1903 AD. Option B is incorrect because Sirmaur Riyasati Praja Mandal was founded in 1940 AD, not 1905 AD. Option D is incorrect because Sirmaur Riyasati Praja Mandal was founded in 1940 AD, not 1944 AD.