Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

a. Sodium-potassium ATPases

b. Ligand-gated channels

c. Voltage-gated channels

d. Leak channels

The correct answer is option d, that is, leak channels.

The cell membrane comprises protein channels known as leak channels, which permits sodium and potassium ions to leak down their concentration gradients. The membranes of the cell are significantly more permeable to potassium ions in comparison to the sodium ions, due to the presence of more K + leak channels than Na + leaks channels.