Nuclear arms race was a key factor in extending the time period of the cold war. The seeds of the hostility between USSR in US began after the end of World War I with the rising of communism in USSR in Stalin rule made it worse.
The only state that did not go was Rhode island so I'm guessing A.
Answer:
the trade of African Americans by boat across the Atlantic and West Indies
Explanation:
It was primarily the "b. formation of the Vietcong in Vietnam" that led the Truman administration to expand the containment doctrine to include Asia, since this was seen as a threat to democratic principles in the west as well.