Since There Is a Larger Concentration of Potassium Ions Inside

Multiple Choice

Since there is a larger concentration of potassium ions inside a neuron,why is the inside of the neuron negative (-70mV) relative to the outside?

A) Potassium ions carry a negative charge.
B) Negatively-charged proteins inside the cell counteract the charge of the potassium ions.
C) The negative sign is just a historical convention.
D) The high concentration of sodium ions outside the cell makes the inside negative by comparison.