Why Correct: Dharmapala, the Pala emperor who ruled from approximately 770-810 CE, established Vikramasila University in present-day Bihar as a major center for Buddhist learning, rivaling Nalanda.
Distractor Analysis: Dhruva was a Rashtrakuta ruler known for his northern campaigns. Devapala succeeded Dharmapala as Pala emperor and expanded the empire but did not found Vikramasila. Ballal Sen was a Sena dynasty ruler of Bengal who came later, around the 12th century.
Takeaway: Vikramasila University was destroyed by Bakhtiyar Khalji's forces around 1200 CE, marking the decline of organized Buddhist education in India.