This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Physiology
The electrical potential difference necessary for a single ion to be at equilibrium across a membrane is best described by the: 
Select and explain. 
A. Goldman equation, B. van't Hoff equation, C. Fick's law, D. Nernst equation
D: Nernst equation
Answer: D: Nernst equation 
Explanation: Ans. D. Nernst equationa. The Nernst equation calculates the membrane potential that develops when a single ion is distributed at equilibrium across a membrane.b. The Goldman equation gives the value of the membrane potential when all permeable ions are accounted for.c. The van't Hoff equation calculates the osmotic pressure of a solution.d. Fick's law refers to the diffusional movement of solute. The permeability coefficient accounts for several factors that determine the ease with which a solute can cross a membrane