The right answer is The Great Council could approve taxes proposed by the monarch.
The English barons, bothered with the King's various failures, on June 10, 1215, take the city of London with the support of the clergy, causing King John to be forced to sign the Magna Carta. This document determined that the English kings had their powers limited, guaranteeing that they could only raise taxes or create new laws upon the approval of a great council composed of nobles. In exchange for this, the barons reinvigorated their oaths of allegiance to King John 4 days later, on June 19, 1215.