This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal System, Subject name: Physiology
[{'content': 'Iron is actively absorbed mainly in:- \nSelect and explain. \nA. Stomach, B. Duodenum, C. Jejunum, D. Ileum', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Almost all iron absorption occurs in the duodenum.', 'role': 'assistant'}]