Final answer:
Engagement refers to the interactions between the U.S. Armed Forces and other nations' forces or agencies to build trust, share information, and maintain influence, key in implementing U.S. foreign policy and defense strategy. Option c. is correct.
Step-by-step explanation:
Engagement is the routine contact and interaction between individuals or elements of the U.S. Armed Forces and other nations' armed forces, or foreign and domestic civilian authorities or agencies, to build trust and confidence, share information, coordinate mutual activities, and maintain influence.
This is a critical element of foreign policy and defense strategy, embodying activities such as using diplomacy to rally allies and isolate threats, marshaling economic power to facilitate or compel cooperation, and maintaining effective armed forces. Such engagement may occur within alliances, like NATO, or in various forms of security cooperation and partnerships across the globe.