Who among the following was the best-known Chahamana ruler?

Correct option is A

The best-known Chahamana ruler is Prithviraja III, also known as Prithviraj Chauhan. He was a king of the Chahamana dynasty and ruled much of present-day Rajasthan in northern India from 1178 to 1192 CE. He is famous for his military exploits and his legendary rivalry with the Ghurid ruler, Muhammad Ghori in Battle of Tarrain.
Ruled  Sapadalaksha from  1177 to 1192 CE with Ajmer (Rajasthan) as capital.
 Also known as Rai Pithora.
 Defeated the Chandelas.
 Fought the Battle of Tarrain against Md Ghuri.