When Does the NCX Stop Moving Ions Across the Membrane

When does the NCX stop moving ions across the membrane?

A) When the energy dissipated by sodium entry equals that associated with movement of calcium ions
B) When the resting membrane potential equals the reversal potential for calcium
C) When the driving force for sodium is different than 0 mV
D) When there is no net driving force for calcium
E) When there is not ATP