Unusual and terrifying themes.
Answer: -Government
-Complex social organization
-Trade and economic activity
Answer: D
Explanation: The United States, South Korea, the Philippines, Australia, Thailand and other anti-communist allies all helped South Vietnam during the Vietnam War. I would choose the U.S. for this question though.
The modern American economy traces it is rooted in the quest of European settlers moving to groups for economic gain in the 16th, 17th, and 18th centuries.