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
Jit equilibrium the concentrations of Cl- inside and outside a cell are 8 mmol/L and 120 mmol/L, respectively. The equilibrium potential for Cl- at 37degC is calculated to be: 
Select and explain. 
A. +4.07 mV, B. -4.07 mV, C. +71.7 mV, D. -71.7 mV
D: -71.7 mV
Answer: D: -71.7 mV 
Explanation: Ans. D. -71.7mVBy substituting in the Nernst equationEi-Eo=61/-1xlog10120/8=-61x1.176=-71.7mV inside the cell.Note that for Cl-, the value for z (valence) is -1