The correct answer is A) China and the Soviet Union supported North Vietnam, while the United States backed South Vietnam, even though the US wasn't directly at war with China or the United States.
That is why the Vietnam War is an example of a proxy war.
When an armed conflict was instigated by two countries that do not directly fight each other, we have a proxy war. Those two major countries use third countries to fight against each other. That was the case of the Vietnam War. During the Cold War years, the Soviet Union wanted to spread Communism in many nations, such as Vietnam. That is why the USSR supported North Vietnam. On the opposite side, the United States wanted to stop the spread of Communism, and that is why it supported South Vietnam.
