Answer:
A. The Soviet Union.
Explanation:
After the end of the Second World War, the Soviet and America decided to divide Korea at the 38th parallel of latitude. The north belonged to the Soviets and South to America.
During the Cold War, North Korea, on June 25, 1950 invaded South Korea with the aim to reunite the country under communism. In the late November 1950s, China entered the scene and backed up North Korea with army force and drove out the US back across the 38th parallel.
Therefore, the correct answer is that agreement with the Soviet Union enabled North Korea to invade the South. Thus option A is correct.
