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: Biochemistry
[{'content': 'Ascorbic acid: \nSelect and explain. \nA. Is a reducing agent, B. Decrease iron absorption, C. Is harmless in high doses, D. Is required for lysyl oxidase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]