Question

which phrase best defines diffusion?
movement through a cell membrane using energy from atp
active transport of particles up a concentration gradient
movement of particles from a region of low concentration to a region of high concentration
movement of particles from a region of high concentration to a region of low concentration

Explanation:

Diffusion is the passive movement of particles down their concentration gradient, from an area of higher concentration to lower concentration, without energy input.

Answer:

movement of particles from a region of high concentration to a region of low concentration