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: Radiology
[{'content': 'The ingredient of the fixing solution (fixer) of the X-ray is: \nSelect and explain. \nA. Hydroquinone, B. Elon, C. Sodium bisulphate, D. Acetic acid', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]