There were three Nebuchadnezzar's who reigned. Assuming that you are talking about Nebuchadnezzar I, he reigned during 1125 - 1104 BC.
The following are correct:
A moat filled with water from the Euphrates River surrounded the city.
Walls around the city provided protection from enemies.
Impeachment is a long process and lots of times doesn't work in time. This happened with Bill Clinton. He was on trial to be impeached but finished his term before he could be removed from office.
Answer:
usually the slaves were chosen based on their race since the whites thought they were better than other races.
