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': 'Which of the following is the best site of absorption\nof calcium? \nSelect and explain. \nA. Proximal segment of small intestine, B. Middle segment of small intestine, C. Ascending colon, D. Ileum', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]