Final answer:
William and Mary accessed the throne through the Glorious Revolution of 1688, becoming the first joint monarchs in English history. They agreed to provisions in exchange for Parliament's recognition, including calling Parliament every three years and giving the source of law to Parliament.
Step-by-step explanation:
William and Mary accessed the throne through the Glorious Revolution of 1688. James II, who openly supported Catholicism, was succeeded by his Protestant daughter Mary and her husband William of Orange. William and Mary ruled jointly in England as the first joint monarchs in English history. In exchange for Parliament's recognition of their reign, they agreed to several provisions, including calling Parliament every three years, limiting the power of the monarch, and giving the source of law to Parliament.