What are some interesting facts about the earth's mantle?

Which of the following terms describes the layers of air surrounding the earth ?

Acivilization exists for several hundred yeaars, developing its own language. such a civilization probably has been: a. farming corn b. suffering from a lack of contact with the outside world. c. isolated by mountains or some other physical barriers. d. starving from lack of trade.

Because its government strictly controls its economy, north korea has a economy. a. command b. mixed c. traditional d. free market