Which best describes dynamic equilibrium?
a.) there is a difference in concentration on either side of the cell membrane.
b.) there is an uneven distribution of particles inside and outside the cell.
c.) particles are moving into and out of the cell, but their concentrations remain stable.
d.) a concentration gradient is forcing water out of the cell and particles into the cell.

C.) Particles are moving into and out of the cell, but their concentrations remain stable.

Explanation:

With respect to a cell, equilibrium refers to the condition of stable concentration or constant amount of substances present in and out of the cell.

The term "dynamic" refers to the fact that the substances are moving in and out of the cell. Hence, dynamic equilibrium is the condition when the cell is exchanging substances with its environment but the concentration of these substances do not change due to exchange.