The correct option is D Hieun Tsang
In the year 643 A.D.Harsha held a great religious assembly in his capital at Kanauj on the bank of the river Ganges. The purpose of the assembly was to highlight the teachings of Buddha. On that occasion, Harsha also wanted to honour the Chinese Master of the Law, Hiuen Tsang.
This grand function was attended by twenty tributary kings. Three thousand Mahayana and Hinayana Buddhists, three thousand Brahmins and Jainas, and one thousand Buddhist scholars from the University of Nalanda attended this assembly. Harsha himself proposed the name of Hiuen Tsang to take the chair. The subject of discussion in the assembly related to Mahayana Buddhism. The assembly continued for long 23 days.