Question

simple diffusion is defined as the movement of
multiple choice
molecules from areas of higher concentration to areas of lower concentration.
molecules from areas of lower concentration to areas of higher concentration.
water molecules across a membrane.
gas molecules across a membrane.
gas or water molecules across a membrane.

Explanation:

Simple diffusion is the passive movement of molecules (like gases, solutes) from a region of higher concentration to lower concentration, driven by the concentration gradient, without energy input. The second option is against the gradient (active transport needs energy for that). The third is osmosis (water diffusion across membrane), fourth and fifth are specific cases, but simple diffusion's core definition is the first option's description.

Answer:

A. molecules from areas of higher concentration to areas of lower concentration.