This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Nernst potential for K 
Select and explain. 
A. 90, B. -90, C. 70, D. -70
B: -90
Answer: B: -90 
Explanation: In case of K+, concentration gradient is outwards and electric gradient is inwards. The Nernst potential of K+ is -90mV.(Ref: Textbook of physiology 5th edition page no.33)