Option b is the correct answer. Rashtrakuta King Govinda III defeated Pratihara ruler Nagabhatta-II in battle of Kannauj as part of his military conquests. Govinda III, who reigned from 793 to 814 CE, achieved significant success during his rule. He conducted a successful northern campaign in 800 CE , capturing important regions by defeating rulers including Nagabhata II of Gurjara-Pratihara, Dharmapala of the Pala Empire, and Chakrayudha, the puppet ruler of Kannauj. This conquest marked Govinda III's supremacy in the northern and eastern parts of India, showcasing his military prowess and expanding the Rashtrakuta Empire's influence.