Which organism is the most primitive? a) bear b) frog c) hippopotamus d) shark

What are charcteristics of lithosphere?

Ecologist have observed a sharp increase of sulfur dioxide in the air . what might be a possible consequence of excessive sulfur dioxide in the air ? a. acid rain b. ozone layer depletion c. ozone layer hole d. increase in sea levels

Facilitated diffusion move large molecules and/or polar molecules across the cell membrane. what does facilitated diffusion use to do this?