The policy of extending a country's empire and influence

Answer: Option A

One word substitute is Imperialism.

Imperialism: a policy of extending a country's power and influence through colonization, use of military force, or other means.
Capitalism: an economic and political system in which a country's trade and industry are controlled by private owners for profit, rather than by the state.
Internationalism: the state or process of being international.
Communism: a theory or system of social organization in which all property is owned by the community and each person contributes and receives according to their ability and needs.