Which of the following wars was fought by the United States?

The chosen answer indicates that all of the wars listed were indeed fought by the United States. Each of these conflicts plays a significant role in American military history.

World War II, which lasted from 1939 to 1945, involved the United States following the attack on Pearl Harbor in 1941. The U.S. fought alongside the Allies against the Axis powers, contributing to significant victories in both the European and Pacific theaters.

The Vietnam War, occurring from the late 1950s into the 1970s, saw the United States deeply involved in the conflict to prevent the spread of communism in Southeast Asia. American combat troops were deployed in significant numbers from 1965 until the withdrawal in 1973, marking a controversial and impactful period in U.S. history.

The Korean War, which took place from 1950 to 1953, was a conflict where the United States led a United Nations coalition to support South Korea against the invasion by communist North Korea. This war solidified the U.S. commitment to contain communism during the Cold War era.

Thus, the selection of 'all of the above' accurately reflects the fact that the United States was a participant in each of these significant conflicts.