The difference in charge between two regions is referred to as:

A) a concentration gradient.
B) a voltage gradient.
C) diffusion.
D) current flow.

Voltage Gradient

Difference in charge between two regions that allows a flow of current if the two regions are connected.

Concentration Gradient

Difference in the relative abundance of a substance among regions of a container; allows the substance to diffuse from an area of higher concentration to an area of lower concentration.

Diffusion

The movement of molecules from an area of higher concentration to an area of lower concentration, a fundamental process in biology and chemistry.