During the Gupta period in ancient India, the official language was Sanskrit. Sanskrit was a standardized language that had a great influence on literature, religion, and administration during this time. It was considered a sacred language and was used for religious scriptures, by scholars, and for official communication.

Pali, Magadhi, and Prakrit are also ancient languages that were spoken during different periods in India. Pali was the language of the Buddhist scriptures, particularly the Tripitaka. Magadhi and Prakrit were regional languages that were prevalent in different parts of India, but they were not the official language of the Gupta period.

In summary, the correct answer is option 4, Sanskrit, as it was the official language of the Gupta period in ancient India.