The correct answer is option 3, Kharavela. Kharavela was a king who ruled over the Kalinga region in present-day Odisha, India, during the 1st century BCE. He is known for his patronage and promotion of Jainism.

Option 1, Bimbisara, was a king of the Magadha kingdom and is associated with the rise of Buddhism, not Jainism.

Option 2, Mahapadma Nanda, was a king of the Nanda dynasty, which ruled over the Magadha kingdom before the rise of the Maurya empire. There is no significant historical evidence to suggest that Mahapadma Nanda was an ardent follower of Jainism.

Option 4, Pulakesin II, was a king of the Chalukya dynasty in South India during the 7th century CE. He was a patron of Shaivism (a sect of Hinduism) and there is no evidence to suggest that he followed Jainism.

Based on historical records, it is clear that Kharavela was the king who was an ardent follower of Jainism among the given options.