Jainism is one of the major religions that originated in ancient India. It was founded by Mahavira, who was born in 6th century BCE. Jainism emphasizes non-violence, truthfulness, and asceticism.

In the given options, we need to identify the kings who were followers of Jainism. Let's analyze each option:

1. Rajaraja I: Rajaraja I, also known as Rajaraja the Great, was a Chola king who ruled from 985 to 1014 CE. He is renowned for his architectural achievements, particularly the construction of the Brihadeeswarar Temple in Thanjavur. Rajaraja I was a patron of Hinduism and promoted Shaivism, a sect of Hinduism that worships Lord Shiva. There is no historical evidence to suggest that he was a follower of Jainism. Therefore, option 1 is incorrect.

2. Chandragupta Maurya: Chandragupta Maurya was the founder of the Mauryan Empire and ruled from 322 to 298 BCE. He was the first emperor to unify most of the Indian subcontinent. Chandragupta Maurya initially followed the teachings of Jainism, and he was a disciple of Jain ascetic Bhadrabahu. However, later in his life, he renounced his kingdom and became an ascetic himself. He is believed to have starved himself to death by observing the practice of Sallekhana, a voluntary fast unto death. Therefore, option 2 is correct.

3. Mahendraverman Pallava I: Mahendraverman Pallava I was a king of the Pallava dynasty who ruled from 600 to 630 CE. The Pallavas were known for their patronage of art and architecture, particularly the rock-cut temples in Mamallapuram. While Mahendraverman Pallava I was a patron of Hinduism and constructed several Hindu temples, there is no evidence to suggest that he was a follower of Jainism. Therefore, option 3 is incorrect.

From the analysis above, we can conclude that only Chandragupta Maurya, among the given kings, was a follower of Jainism. Hence, the correct answer is option C: 2 and 3 only.