Which Must Be True for an Ion to Be at Equilibrium

Multiple Choice

Which must be true for an ion to be at equilibrium?

A) The concentrations on both sides of the membrane must be equal.
B) The electrical gradient must match the concentration gradient in the opposite direction.
C) The neuron's membrane potential must be negative.
D) The neuron's membrane potential must be positive.
E) The permeability of the ion must be zero.