What made the climate of northern africa change from tropical to grasslands and then to desert?

I’m annoyed but glad that my history teacher left and quit her job as a teacher to become a flight attendant

Considering the benefits and drawbacks of the different types of money as well as the gold standard, do you agree or disagree with the us government’s decision to discontinue the gold standard? justify your response.

Characteristics of what type of economic system are being described below? 1.economy in which some/all of the basic economic questions answered by central authority 2.trade generally limited to what is produced through the influence of the government a. command economies. b. market economies. c. traditional economies.