This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Physiology
[{'content': 'Hardest tissue in humans \nSelect and explain. \nA. Enamel, B. Bone, C. Muscle, D. Skin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: a (Enamel)Hardest tissue in humans is enamel.', 'role': 'assistant'}]