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
[{'content': 'Nernst potential for K \nSelect and explain. \nA. 90, B. -90, C. 70, D. -70', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 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)', 'role': 'assistant'}]