This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and Reproduction, Subject name: Physiology
[{'content': 'Calcium absorption is from: \nSelect and explain. \nA. Proximal small intestine, B. Distal ileum, C. Middle small intestine, D. Ascending colon', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Proximal small intestine(Ref: Ganong, 25th ed/p.375)Active calcium absorption occurs mainly in the proximal small bowel (duodenum and proximal jejunum)', 'role': 'assistant'}]