Which of the Following Is True About the Movement of Ions

Multiple Choice

Which of the following is true about the movement of ions across excitable living membranes?

A) Ions always move actively across membranes through leakage channels.
B) Ions always move from an area of higher concentration to an area of lower concentration
C) Sodium gates in the membrane can open in response to electrical potential changes.
D) Ions always move passively across membranes.