Because the constitution requires state and national government to be united, but each having it's own power. The constitution also states that no one person should have too much power, nor should any branch or state have too much power, so the power is split evenly.
D. The Soviet Union and Chinese helped Korean communists gain power in the north.
Some think it was called this because of how the skin turned dark at the late stages of the disease, but it was more likely called "Black" to reflect the dark and horrible time in history.
