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': 'The DMF index when used for primary teeth, uses \nSelect and explain. \nA. Upper case letters, B. Title case letters, C. Lower case letters, D. Sentence case letters', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]