Explanation:

- The main centre of power for the Gupta dynasty was Patliputra (present-day Patna).

- Patliputra was the capital for several major dynasties, including the Mauryas and Guptas. It became a vibrant political, economic, and cultural hub.

- Prayag (Allahabad) was a significant city for religious and occasional administrative purposes, but it was not the main centre of Gupta power.

- Ujjain was another important city during the Gupta period, prominent for trade and sometimes governance, but not the central seat of power.

- Kashi (Varanasi) was revered for religion and learning but not a political capital.

Correct Answer: Option 3, Patliputra