Answer:
middle class whites tended to leave the cities to buy affordable houses in the suburbs,While blacks migrated north to unban areas
(im not sure )
The Chinese constructed the "Great Wall of China." Some difficulties they had to face was possible invasion whilst they were vulnerable and focused on building the wall, invading animals, foreign lands, malfunctions with the building materials, (great stone blocks,) and possible death, since they were building in sometimes treacherous conditions.
