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': 'When assessing tooth mobility the best indicator is \nSelect and explain. \nA. Condition of gingival periodontal fibers, B. Horizontal crown displacement, C. Root displacement within the remaining periodontal ligament, D. Amount of calculus and plaque present', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]