The best option in terms of the government in Spanish colonies would be that
"c. large regions run by a Viceroy [were] appointed by the king,"
since these represented a great source of revenue for the crown.
Explanation:
A viceroy is a person who is appointed by a king to be answerable of a rustic or province. Once a rustic is dominated by a monarch a king or queen and governs the colonies or provinces, the monarch cannot govern all those remote areas in person. The king or queen appoints a representative to rule over the colony or province.
