What is the reasoning behind the United States' intervention into Vietnam's politics, thus joining the Vietnam War?

Question 6 options:

They United States wanted to end the tyrannical power of North Vietnam.

The United States believed that if North Vietnam was not stopped communism would spread to all other neighbors in South East Asia.

The Cambodian Government requested the US intervene to stop the crimes against humanity being committed by the South Vietnamese Government.

Question 7
The United States successfully halted the spread of communism to South Vietnam.

Question 7 options:
True
False