Kanishka was

the king of Kushan dynasty
a great conqueror but later became a follower of Buddha
the only ruler of India whose territory extended up to central Asia
All of the above

The correct answer is D. All of the above.

Kanishka was the most famous ruler of the Kushan dynasty, which ruled over a large part of Central Asia and northern India from the 1st to the 3rd centuries CE. He was a great conqueror who extended his empire to include much of present-day Afghanistan, Pakistan, and northern India. He was also a patron of Buddhism and is credited with convening the Fourth Buddhist Council.

Kanishka was born in the Kushan capital of Purushapura (modern-day Peshawar, Pakistan). His father, Vima Kadphises, was the founder of the Kushan dynasty. Kanishka came to power in the early 2nd century CE and quickly established himself as a powerful ruler. He conquered much of Central Asia and northern India, and his empire stretched from the Oxus River in the west to the Ganges River in the east.

Kanishka was a great patron of Buddhism. He is credited with convening the Fourth Buddhist Council in Kashmir in the year 100 CE. This council was attended by Buddhist monks from all over the Buddhist world, and it resulted in the standardization of Buddhist doctrine. Kanishka also built many Buddhist temples and stupas, and he is said to have given away large amounts of money to the Buddhist community.

Kanishka was a tolerant ruler who allowed people of all religions to practice their faith freely. He is said to have been a follower of both Buddhism and Hinduism. He was also a patron of the arts and sciences, and his reign was a time of great cultural and intellectual flourishing.

Kanishka died in the early 3rd century CE. He was succeeded by his son, Vasudeva I. The Kushan dynasty continued to rule over Central Asia and northern India for several more centuries, but it never regained the power and influence that it had under Kanishka.