This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Which of the following would cause an immediate reduction in the amount of potassium leaking out of a cell? 
Select and explain. 
A. Increasing the permeability of the membrane to potassium, B. Increasing (hyperpolarizing) the membrane otential, C. Decreasing the extracellular potassium concentration, D. Reducing the activity of the sodium-potassium pump
B: Increasing (hyperpolarizing) the membrane otential
Answer: B: Increasing (hyperpolarizing) the membrane otential 
Explanation: The amount of potassium leaking out of the cell depends on its driving forces and its membrane conductance. The driving forces are the membrane potential and the concentration gradient. Hyperpolarizing the membrane makes the inside of the cell more negative and therefore, makes it more difficult for potassium to flow out of the cell. Increasing the permeability of the membrane to potassium or decreasing the extracellular potassium concentration increases the flow of potassium out of the cell. Altering the activity of the sodium-potassium pump or the extracellular sodium concentration has no immediate effect on the flow of potassium across the membrane. However, decreasing the activity of the sodium-potassium pump will ultimately depolarize the membrane, increasing the flow of potassium out of the cell.