Option a is the correct answer. Sungyun came to India in 515 CE along with the monk 'Hui Zheng, Fa Li, and Zheng Fouze', during the reign of Buddhist Empress Hu who belongs to the 'Northern Wei Dynasty. Song Yun, who was originally from Dunhuang in China. In 518 they left Wei capital Luoyang and returned in the winter of 520 CE along with 117 Mahayana Buddhist texts. Fortunately, several valuable pieces of information about their journey have been conserved in Loyang Jielanji of Yang Xianzhi and other texts. He visited the Swat valley in northwestern India and wrote the account of the Gandhara dynasty.