This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Transpo Processes, Subject name: Physiology
[{'content': 'In the sodium-calcium exchanger (NCX), the ratio of Na+ : Ca++ exchange per event is: \nSelect and explain. \nA. 6:01, B. 3:01, C. 1:01, D. 1:03', 'role': 'user'}, {'content': 'Answer: B \nExplanation: NCX (sodium and calcium exchanger) is present in the myocardial fiber. It exchanges 3 Na+ with 1 Ca++. That is, 3 sodium ions are moved out of the cell for every 1 calcium ion brought in (L type Ca channels).', 'role': 'assistant'}]