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': "Score 0-0.4 in Dean's index indicates \nSelect and explain. \nA. Negative mottling, B. Slight mottling, C. Moderate mottling, D. Severemottling", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]