The correct answer is C. Hieun Tsiang.
Hieun Tsiang was a Chinese Buddhist monk who traveled to India in the 7th century CE. He wrote a detailed account of his travels, which included descriptions of the Indian people, culture, and religion. His work is an important source of information about India during this period.
Harshavardhan was an Indian emperor who ruled in the 7th century CE. He was a patron of the arts and literature, and his court was a center of learning.
Selucas Nicator was a Macedonian general who founded the Seleucid Empire after the death of Alexander the Great. He ruled over much of the Middle East, including parts of India.
Megasthanese was a Greek ambassador who was sent to India by Seleucus Nicator in the 4th century BCE. He wrote a book about India, which is now lost.
I hope this helps!