Explanation:

- Panini (Option 1): He was an ancient Sanskrit grammarian, around 4th century BCE. Panini’s work ‘Ashtadhyayi’ contains the first clear reference to ‘Bharata’ as a territorial region, not just as a mythological or dynastic term.

- Patanjali (Option 2): A later Sanskrit grammarian and commentator who lived around 2nd century BCE, but does not provide the earliest reference to Bharata as a region.

- Herodotus (Option 3): A Greek historian, known as the ‘Father of History’. He mentions ‘India’, not ‘Bharata’, in his work.

- Hieun-Tsang (Xuanzang) (Option 4): A Chinese Buddhist monk and traveler in the 7th century CE. He visited India and used the name 'Bharata', but long after Panini.

Correct Answer:

Option 1 - Panini