The correct option is:
C. viceroy.
A Viceroy is an official appointed to rule a country, colony, city, province, or sub-national state, as the deputy of the monarch of the territory. A viceroy's territory may be called a viceroyalty.
Viceroy is not a noble rank as much as a form of royal appointment. However, a person enacted as viceroy often also holds a noble title.