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
Which of the following is the first electron donor among the component of developer? 
Select and explain. 
A. Phenidone, B. Hydroquinone, C. Ammonium thiosulphate, D. Sodium sulfite
A: Phenidone
Answer: A: Phenidone 
Explanation: None