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': 'Which ion causes repolarization? \nSelect and explain. \nA. Magnesium, B. Calcium, C. Potassium, D. Sodium', 'role': 'user'}, {'content': 'Answer: C \nExplanation: When potassium goes from inside to outside it causes rapid repolarization. (REF: TEXTBOOK OF MEDICAL PHYSIOLOGY GEETHA N 2 EDITION, PAGE NO - 26)', 'role': 'assistant'}]