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: Dental
[{'content': 'On microscopic examination enamel rods have: \nSelect and explain. \nA. Key hole appearance in cross-section, B. Paddle appearance in cross-section, C. Lanullate appearance in cross-section, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Enamel rods appear in cross section as keyholes (or) fish scales (or) staggered arches (or) stacked arches.', 'role': 'assistant'}]