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 is the poorest source of calcium among the following? \nSelect and explain. \nA. Rice, B. Human milk, C. Egg yolk, D. Cow's milk", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]