The correct answer is option 'A', Panini's Ashtadhyayi.

Panini's Ashtadhyayi:

- Panini's Ashtadhyayi is a renowned ancient Sanskrit grammar text. It is considered one of the earliest and most comprehensive works on grammar in the world.
- The Ashtadhyayi consists of eight chapters, each divided into four sections called padas. It covers various aspects of grammar, including phonetics, morphology, syntax, and semantics.
- While the primary focus of the Ashtadhyayi is on linguistics and grammar, it also contains references to various aspects of Indian culture, religion, and mythology.

Deification of Vasudeva:

- The deification of Vasudeva, a human hero, is mentioned in Panini's Ashtadhyayi.
- Vasudeva is a significant figure in Hindu mythology and is considered an incarnation of Lord Vishnu, the preserver and sustainer of the universe.
- The deification of Vasudeva implies that he was revered and worshipped as a divine being, elevating him to a status of divinity.
- This reference to the deification of Vasudeva in the Ashtadhyayi indicates the early recognition of his divine nature and the development of a religious cult around him.

Significance:

- The mention of the deification of Vasudeva in Panini's Ashtadhyayi provides insights into the early development of religious beliefs and practices in ancient India.
- It suggests that the deification of human heroes and their elevation to divine status was an important aspect of the religious and cultural landscape of that time.
- This practice of deifying human heroes is also seen in other ancient Indian texts and mythologies, such as the Mahabharata and the Ramayana.
- The deification of Vasudeva as a divine being reflects the belief in the divinity and spiritual potential of human beings, as well as the concept of avatars or incarnations of gods in Hinduism.
- This reference also highlights the early origins of Vaishnavism, a major sect within Hinduism that worships Lord Vishnu and his avatars, including Vasudeva.

In conclusion, the earliest reference to the deification of human hero Vasudeva is found in Panini's Ashtadhyayi. This reference sheds light on the early development of religious beliefs and practices in ancient India, particularly in relation to the recognition of divine qualities in human beings and the concept of avatars.