Under Which of the Following Conditions Would the Current-Voltage Relation

Under which of the following conditions would the current-voltage relation for a channel be nonlinear?

A) When the voltage across the plasma membrane is very negative
B) When the ion concentrations on either side of the channel are symmetrical, or because the channel itself is nonrectifying
C) When the ion concentrations on either side of the channel are not symmetrical, or because the channel itself is rectifying
D) When the equilibrium potential for the channel is at zero millivolts
E) When the mean open time of the channel randomly varies