Sympathetic Stimulation Increases the Heart Rate by

Sympathetic stimulation increases the heart rate by

A) just increasing ion influx, thus increasing the rate of depolarization.
B) just increasing the permeability to Ca²⁺.
C) just increasing the permeability to K⁺.
D) just decreasing the permeability to Ca²⁺.
E) increasing the permeability to K⁺ and decreasing the permeability to Ca²⁺.