Prithviraja III defeated an Afghan ruler named ______ in 1191.

Sultan Muhammad Ghori

The correct answer is Option 4- Sultan Muhammad Ghori

Prithviraja III defeated Sultan Muhammad Ghori in 1191 in the First Battle of Tarain.

Sultan Muhammad Ghori was a powerful ruler of the Ghurid dynasty who invaded India several times. He was defeated by Prithviraja III in the First Battle of Tarain, but he returned the following year with a larger army and defeated Prithviraja III in the Second Battle of Tarain.

The defeat of Prithviraja III at the Second Battle of Tarain marked the beginning of Muslim rule in India.