Option C, the ion channels that are open in the cell
Explanation:
Ion channels work on the principle of identification of size of the pore.
The plasma membrane of neuron is slightly permeable to Na+ ion while it is highly permeable to K+ ion. The concentration of Na+ ion is higher outside the cell while it is lower inside the cell while the concentration of K+ ion is higher on the inner side of the cell as compared to the outer side of the cell. The ion gate is responsible for maintain this equilibrium. When sodium potassium pump works (or ion gate is considered open), it causes movement of ions against the gradient through active transportation.
