Explanation:

- Pulakesin II:

- Correct Answer.

- Harshavardhana was defeated by Pulakesin II when he attempted to invade the Chalukya kingdom in the Deccan.

- This victory established Pulakesin II's dominance and highlighted his military prowess.

- Mangalesha:

- Pulakesin II's uncle and the second ruler of the Early Chalukya dynasty.

- Known for expanding the Chalukya territory but not directly involved in defeating Harshavardhana.

- Kirtivarman I:

- The father of Pulakesin II and the first ruler of the Early Chalukya dynasty.

- He expanded the kingdom significantly but passed away before Harshavardhana's campaign.

- Vikramaditya I:

- Another ruler in the Chalukya dynasty but after Pulakesin II's era.

- Not involved in the conflict with Harshavardhana.