Which is the best definition for empire? a. an area where independent states join together for the purpose of trade but retain self-rule b. a region where a people have developed certain charactersistics, such as goverment and trade c. a goverment in which a single ruler makes and enforces the laws of the land d. an area or political unit which formerly independent states are under the control of one ruler c. a goverment in which a single ruler makes and enforces the laws of the land d. an area or political unit which formerly independent states are under the control of one ruler