Final answer:
After North Korea invaded South Korea, the U.S. decided to step up aid to France in Indochina to prevent the spread of communism. The U.S. provided financial and military support to the French forces in their fight against the Viet Minh.
Step-by-step explanation:
Following North Korea's invasion of South Korea in 1950, the United States intensified its support for the French in Indochina. This action was driven by the fear of the spread of communism in Asia. The Truman administration, under its policy of containment, saw the conflict in Korea as part of a larger communist threat and responded by increasing military and financial aid to the French forces fighting against the Vietminh in Vietnam.
The reasoning behind this was to prevent the domino effect, where the fall of one country to communism could lead to neighboring countries also succumbing to communist ideology. This move marked a significant escalation in U.S. involvement in Vietnam, laying the groundwork for deeper engagement in the conflict in the years to come, eventually leading to direct American military involvement in the region.
The correct answer is C. The United States decided to step up aid to the French in Indochina.