Which layer is a solid made mostly of nickel and iron?
a. crust
b. astenosphere
c. inner core
d. none of the above

Most countries in the middle east must import a majority of their a. gasoline b. oil c. food d. water

How can minerals crystallize from materials dissolved in water? check all that apply.

Fossils of glossopteris, an extinct fern, were discovered on which continents to support the theory of continental drift? check all that apply.