Option d is the correct answer. One of the most famous students of Nalanda was the Chinese traveler Hiuen Tsang, also known as Xuanzang. Hiuen Tsang visited India from 629 CE to 645 CE, during which he traveled extensively across the subcontinent. He visited Nalanda in 637 CE and stayed there for about five years. He studied under the guidance of eminent teachers, such as Shilabhadra and Dharmapala. Hiuen Tsang also wrote a detailed account of his studies and experiences at Nalanda in his famous work Si -Yu-Ki or Records of the Western World. Hiuen Tsang's writings provide valuable information about the history, geography, society, religion, and culture of India during Harsha's reign. Important Tips Taxila was an ancient city in present-day Pakistan, which was a center of learning, culture, and trade. Taxila was founded by the Achaemenid Persians in the 6th century BCE and later ruled by various dynasties, such as the Mauryas, the Indo-Greeks, the Kushanas, and the Guptas. Taxila had a famous university that offered courses in various subjects, such as law, medicine, art, and religion. Taxila was also a hub of Buddhism and had many monasteries and stupas. Vikramshila was a famous Buddhist university in ancient India, which was located in present-day Bihar. Vikramshila was founded by Dharmapala, the king of the Pala dynasty, in the 8th century CE. Vikramshila was a center of learning, culture, and religion, and specialized in the study of Tantric Buddhism. Vikramshila had a large campus that housed many temples, libraries, and dormitories.