The correct answer is the Gupta period.
The Gupta period was a golden age of Indian art and culture. It was during this time that the art of stone carving in Bihar reached its peak. Some of the most famous examples of Gupta-era stone carving can be found in the temples of Nalanda and Bodh Gaya.
The Mauryan period was a time of great political and economic expansion in India. However, it was not a time of great artistic achievement. The Mauryans were more interested in building roads, canals, and other infrastructure than in creating works of art.
The Pala period was a time of political and economic decline in India. However, it was also a time of great artistic achievement. The Palas were patrons of the arts, and they commissioned many beautiful works of art, including stone carvings.
The Mughal period was a time of great cultural and religious diversity in India. The Mughals were tolerant of other religions, and they commissioned works of art that reflected this diversity. However, they did not produce any great works of stone carving.
In conclusion, the art of stone carving in Bihar dates back to the Gupta period. The Gupta period was a golden age of Indian art and culture, and it was during this time that the art of stone carving in Bihar reached its peak.