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: ENT
[{'content': 'Fluid, which has high potassium and low sodium contents, is - \nSelect and explain. \nA. CSF, B. Ectolymph, C. Endolymph, D. Pleural fluid', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]