Question

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

Explanation:

Dynamic equilibrium in a cellular context means that particles are in constant motion across the cell - membrane, but the overall concentrations on both sides remain the same. This is because the rate of particles moving into the cell is equal to the rate of particles moving out of the cell.

Answer:

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