The correct answer is A. Ajai Chand.
Ajai Chand was the founder of the Nalagarh state in 1100 AD. He was a descendant of the Chauhans of Ajmer. He established the state in the Sivalik Hills, which are located in the present-day state of Himachal Pradesh. The Nalagarh state was ruled by the Chand dynasty for over 700 years. The last ruler of the Chand dynasty was Sansar Chand. He was defeated by the British in 1819 and the state was annexed by the British.
Option B, Jaspal, is incorrect. Jaspal was the son of Ajai Chand and the second ruler of the Nalagarh state. He ruled from 1120 to 1150 AD.
Option C, Kahn Chand, is incorrect. Kahn Chand was the grandson of Ajai Chand and the third ruler of the Nalagarh state. He ruled from 1150 to 1180 AD.
Option D, Sansar Chand, is incorrect. Sansar Chand was the last ruler of the Nalagarh state. He ruled from 1770 to 1819 AD.