Answer:
с . The United States entered the wars to stop the spread of communism.
Explanation:
The Korean War was fought between 195-53 while the Vietnam War was fought from 1955-75. And in both wars, the parties involved included not only the namesake countries but also foreign powers such as the United States, Soviet Union, and China.
But the one major similarity between these wars was that the United States joined the war to prevent an all-out spreading of communism. With the Chinese and Soviet forces supporting communism, victory in these wars would mean the spread of a communist government. And it was this want of preventing such a government that the United States got involved in it.
Thus, the correct answer is option C.