On the Frontiers of the Spanish Empire in America, the Main

On the frontiers of the Spanish Empire in America, the main instruments) of colonization was

A) the religious missions to indoctrinate and control the natives.
B) the strong military garrisons and fortifications to keep enemies at bay.
C) the sugar plantations to keep those at the bottom busy with work and away from rebellious ideas.
D) the creation of a community in which all participants had the same rights.