Explanation:

- Kanishka: He was a prominent ruler of the Kushan dynasty, known for his patronage of Buddhism and establishing a vast empire in Central and South Asia.

- Samudragupta: He was a ruler of the Gupta dynasty, celebrated for his military conquests and the expansion of his kingdom, often referred to as the "Napoleon of India."

- Dhruva: He was indeed a ruler of the Rashtrakuta dynasty, known for his military campaigns and consolidation of power in the Indian subcontinent.

- Ashoka: A legendary emperor of the Maurya dynasty, renowned for his conversion to Buddhism and efforts to spread its teachings across Asia.