Question

Which of the following led to the United States' entry into the Korean War?

A. the United States' defense alliance with North Korea
B. China's desire to reunify Korea as a communist nation
C. a North Korean attack on U.S. naval ships in the Gulf of Tonkin
D. passage of a United Nations decision to condemn North Korean aggression

Answer 1

Its not A, America never had an alliance with NK.
Its not B. I took to test and B was wrong. 
Its not C, the Gulf of Tonkin incident was during the war in Vietnam. 

It has to be D. 

Hope my suffering helped :)

Answer 2

Answer:

passage of a United Nations decision to condemn North Korean aggression