Fa-Hien
- Fa-Hien was a Chinese Buddhist monk who visited India during the reign of Chandragupta II in the 5th century AD.
- He traveled to India in search of Buddhist scriptures and spent several years studying and translating them.
- Fa-Hien's visit to India is recorded in his travelogue, "Record of Buddhistic Kingdoms", which provides valuable insights into the social, cultural, and religious aspects of ancient India.

Megasthenes
- Megasthenes was a Greek ambassador and historian who visited India during the reign of Chandragupta Maurya in the 4th century BC.
- He was sent to the Mauryan court by Seleucus I Nicator, the successor of Alexander the Great, and his account of India is recorded in his book, "Indika".
- Megasthenes' visit to India is significant as it provides one of the earliest and most detailed accounts of ancient Indian civilization, including its political organization, social structure, and cultural practices.

I-Tsing (Yijing)
- I-Tsing was a Chinese Buddhist monk who visited India during the reign of Harsha Vardhana in the 7th century AD.
- He traveled to India to study Buddhist philosophy and scriptures and spent several years in various Buddhist monasteries.
- I-Tsing's visit to India is documented in his travelogue, "A Record of the Buddhist Religion as Practiced in India and the Malay Archipelago", which provides valuable information about the state of Buddhism in India during that time.

Hiuen-Tsang
- Hiuen-Tsang, also known as Xuanzang, was a Chinese Buddhist monk who visited India during the reign of Harsha Vardhana in the 7th century AD.
- He undertook a perilous journey to India in search of Buddhist scriptures and spent many years studying and translating them.
- Hiuen-Tsang's visit to India is recorded in his travelogue, "The Great Tang Records on the Western Regions", which is one of the most important historical sources on ancient India.
- His writings provide valuable insights into the political, social, and cultural aspects of India during the Gupta and post-Gupta periods.

Correct Chronological Sequence: 3, 1, 4, 2
- Megasthenes visited India in the 4th century BC.
- Fa-Hien visited India in the 5th century AD.
- Hiuen-Tsang visited India in the 7th century AD.
- I-Tsing visited India also in the 7th century AD.

Hence, the correct chronological sequence of the visits of these individuals to India is 3, 1, 4, 2.