SAT World History Practice Question

The United Nations deployed an international military force in South Korea in 1950 primarily because

1. A.North Korea threatened to launch a nuclear attack against South Korea
2. B.North Korean and Chinese ships attacked South Korean ships in the Yellow Sea
3. C.North Korean troops had crossed the 38th parallel into South Korean territory
4. D.North Korea acquired nuclear weapons from the Soviet Union
5. E.North Korea was on the verge of overthrowing the South Korean government