Why are there different skin tones and races in this world?

How does central place theory explain patterns in the size and distribution of cities?

Ascientist is explaining how background cosmic radiation gives evidence of the big bang theory. she says that radiation has been detected everywhere equally as heat in the universe and is increasing. this has been shown to be residual radiation from the big bang. what error did the scientist make?

Which of the following best describes the circumstance under which countries block the importation of certain products into their country? a. importation blockade b.trade barrier c.trade inhibitor d. domestic protection act