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': 'Periodontal ligament is \nSelect and explain. \nA. Narrower on mesial surface, B. Wider on mesial surface, C. Equal on both the surfaces, D. Wider in the anterior teeth', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]