Explanation

Ratnavali (a Sanskrit romantic comedy) was authored by the Pushyabhuti emperor Harshavardhana (r. 606–647 CE), who also wrote Nagananda and Priyadarshika. The Harshacharita (option A) and Kadambari (option B) are the works of Harsha's court poet Banabhatta, not of Harsha himself. The Gitagovinda (option D) is the celebrated 12th-century work of Jayadeva. Hence option C.