Answer the following question given this paragraph: 

Molecules move from an area of high concentration to an area of lower concentration until an equilibrium is met. The molecules continue to cross the membrane at equilibrium, but at equal rates in both directions.


Q: Molecules move from an area of high concentration to an area of lower concentration until an what is met?

 Choices:

- respiration

- freezing point

- oxidation

- equilibrium

A:
equilibrium
