Which elements are found in a high proportion in earth’s crust?
a. aluminum and iron
b. oxygen and silicon
c. calcium and sodium
d. potassium and magnesium

The vegetation that thrives in the tundra is limited to a. mosses, barley, wheat, and corn. b. coniferous trees. c. dwarf shrubs, mosses, lichen, potatoes, and beans. d. mosses, lichen, algae, and dwarf shrubs.

Which season occurs in the northern hemisphere when the sun is at its lowest point in the sky

Which of the following is an example of relocation diffusion