The answer is A, natural selection.
Nationalism and imperialism were major factors to the world war 1. that lead to some conflicts between nations. imperialism also contributed to start world war 1 because the European nations attacking and conquering different areas of Africa and Euro nations attacking other Euro nations for African Territory.
After fighting the war in Korea, the US had learned that communism would spread. In order to keep with their policy of containment, they had to rush in and stop Viet Cong from spreading communism (much like the domino theory that the US had). Had Viet Cong not wanted to bring about communism, there would be no need for invasion, and the domino theory would have yet to be proven.
:)
(false) Known in the north as the Battle of Bull Run and in the South as the Battle of Manassas, this battle, fought on July 21 1861 in Virginia was the first major battle of the Civil War. It was a Confederate victory.
