What made the climate of northern africa change from tropical to grasslands, and then to desert? tilt of the earth's axis the nile river ice ages overpopulation of the region

Which of the following describes an effect of world war ll on the united states economy a. automobile companies produced a record number of cars b. many factories had to expand to produce military equipment c. the airplane industry suffered as the allies began using airplanes in combat d.cities with shipyards declined because so many ships had been sent overseas.