Explanation:

- Banabhatta was a classical Sanskrit scholar and poet.

- Harshacharita is a biographical work narrating the life of Emperor Harsha.

- It is known for its prose style and intricate expressions.

- Option 1: Sanskrit - This is the correct answer. Banabhatta composed "Harshacharita" in Sanskrit.

- Option 2: Pali - A language used primarily in Buddhist scriptures, not relevant here.

- Option 3: Tamil - A Dravidian language, unrelated to Banabhatta's works.

- Option 4: Prakrit - A group of related dialects, not used by Banabhatta for this work.