This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc., Subject name: Physiology
[{'content': 'Ascorbic acid is a potent enhancer of iron absorption because it: \nSelect and explain. \nA. Enhances the absorption of heme iron, B. Enhances the activity of heme oxygenase, C. Is a reducing agent, thereby helping to keep iron in the ferrous state, D. Decreases the production of ferritin by enterocytes', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C. Is a reducing agent, thereby helping to keep iron in the ferrous stateAscorbic acid enhances iron absorption mostly by its reducing capacity, keeping iron in the ferrous state. Ascorbic acid does not enhance heme iron absorption, nor does it affect heme oxygenase activity or the production of ferritin or transferrin.', 'role': 'assistant'}]