During the repolarization phase of an action potential, the rapid efflux of potassium ions is primarily driven by which of the following mechanisms?

1. A.Activation of voltage-gated ${\text{K}}^{+}$ channels and the electrochemical gradient
2. B.Inactivation of voltage-gated ${\text{Na}}^{+}$ channels and active transport via ${\text{Na}}^{+}/{\text{K}}^{+}$ pump
3. C.Opening of ligand-gated chloride channels causing hyperpolarization
4. D.Closure of voltage-gated ${\text{K}}^{+}$ channels and passive diffusion of ${\text{Na}}^{+}$ ions