The political theory that people form governments for their mutual protection and that government rules only with the consent of those people is known as
a. communism.
b. socialism.
c. divine right theory.
d. social contract theory.

Generally speaking, the political theory that people form governments for their mutual protection and that government rules only with the consent of those people is known as "d. social contract theory," since this was one of the main components of Enlightenment thinking and helped inspire the formations of nations such as the US.