to me letter C best describes the role of Viceroys in Spain's American empire :)
hope this helps :)
Generally speaking, a viceroy is someone who runs a country, colony, city, or similar setting in the name of the king or monarch that owns the territory. It changed a little bit in the Americas, where viceroys would be those who govern the highly populated and wealthy regions.
Nothing in that description fits A, B or D.
So the correct answer is:
C. Viceroys watched over the king's lands, increased his wealth, and carried out his will.