The correct answer is D. Prithviraj Chauhan.
Prithviraj Chauhan was the last Hindu ruler of the Chauhan dynasty of Ajmer. He was defeated and killed by Muhammad Ghori in the First Battle of Tarain in 1192. His death marked the end of Hindu rule in Northern India.
Harshavardhana was a Hindu emperor who ruled over the northern Indian subcontinent in the 7th century. He was a powerful and successful ruler who expanded his empire to include much of present-day India, Pakistan, and Bangladesh.
Mahipal was a Hindu king who ruled over the Pratihara dynasty in the 10th century. He was a powerful and successful ruler who expanded his empire to include much of present-day India.
Anangpal II was a Hindu king who ruled over the Tomara dynasty in the 11th century. He was a powerful and successful ruler who expanded his empire to include much of present-day India.
All three of these rulers were important figures in Indian history, but only Prithviraj Chauhan is known as the last Hindu ruler of Northern India.