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': 'Study of oral tissue by decalcification method is useful for: \nSelect and explain. \nA. Enamel., B. Pulp., C. Cementum., D. PDL.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Study of oral tissue by decalcification method is not useful for enamel, pulp, pdl.', 'role': 'assistant'}]