The Time Constant for the Decay of Whole-Cell Sodium Current

The time constant for the decay of whole-cell sodium current is different than the time course of single sodium channel inactivation. Why?

A) The sodium current depends on the probability of sodium channel activation.
B) The time course for sodium channel inactivation is longer than the sodium current.
C) The sodium current decays more slowly because of leak channels.
D) The sodium current decay depends on the time course of sodium channel inactivation.
E) The sodium current decays more rapidly as more sodium channels inactivate.