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': 'Most diffusable ion in excitable tissue is - \nSelect and explain. \nA. Na+, B. K+, C. PO4-, D. Cl-', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Points to note\nConcentration of ions\n\nNa+ concentration higher in ECF \nK+ concentration higher in ICF \nCl- concentration higher in ECF\nK+ leak channels allow K+ to move from ICF to ECF\nNa+ is prevented from entering the cell.\nThus diffusion is highest for K+, then Cl- and least for Na+, when the cell is at rest.', 'role': 'assistant'}]