What was the importance to an artist of a papal invitation to rome?

Invitation to serve the papacy was a privilege. Not every one were given the opportunity to serve.

The papacy was moved to the Vatican Palace from the Lateran Palace. Only the best architects and artists were gathered to build Vatican as place for pilgrims and processions similar to imperial Rome. Even after their service, these artist enjoyed increased funding and commissions from patron.

The answer is d.  the north had organized schools, whereas the south had few organized schools.