This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Excitable tissue at rest is least permeable to \nSelect and explain. \nA. Na+, B. K+, C. Ca++, D. CI-', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Points to note\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0Concentration of ions\n\nNa+\xa0concentration higher in ECF \nK+\xa0concentration higher in ICF \nCl-\xa0concentration higher in ECF\n\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0K+\xa0leak channels allow K+\xa0to move from ICF to ECF\n\nNa+\xa0is prevented from entering the cell.\n\nThus diffusion is highest for K+, then Cl-\xa0and least for Na+, when the cell is at rest.', 'role': 'assistant'}]