"A. The English king made claims to the French throne" is a reasonable answer but it should be noted that the origin of this war is very complex and many people are still guessing.
Because of immigrants and culture and religion
The answer is: b. to prevent the spread of communism in Southeast Asia
After the Geneva Accords divided Vietnam into South and North Vietnam, a group called the Vietcong started a war against the South Vietnam government. Meanwhile, America was sending supplies and a small amount of troops to South Vietnam to support the new democratic country. However, when the communist North Vietnamese defending boats attacked American destroyers, it caused a war with North Vietnam. The US also got involved to stop communism from expanding from North to South Vietnam.
