Answer:
A. He wanted to prevent the advance of communism.
Explanation:
The attack of North Korea on its neighbor was interpreted by the Truman administration as part of a plan of communist expansion in Asia. US top officials in Washington were convinced that the USSR had to be behind it. It was June 1950, and just months before, the Chinese communists had won the Chinese civil war and taken the whole mainland. A recent strategic assesment had left Korea out of the strategic ring of defense in Asia for the USA, but guiding his actions by the tenets of the containment doctrine, Harry Truman decided to oppose this communist aggressive move and plans for expansion and export of revolution. Communism had to be contained. So, Washington got approval for a military intervention by the UN and sent troops to Korea.
