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': 'Which of the following is the first electron donor among the component of developer? \nSelect and explain. \nA. Phenidone, B. Hydroquinone, C. Ammonium thiosulphate, D. Sodium sulfite', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]