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': 'An important clinical feature of a concussed tooth is: \nSelect and explain. \nA. Tooth is markedly tender to percussion, B. Tooth is displaced from the socket, C. Evidence of haemorrhage at gingival margin, D. Clinically crown appears shorter', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Concussion\xa0\n\nTooth is not displaced.\nMobility is not present.\nTooth is tender to percussion because of edema and hemorrhage in the periodontal ligament.\nPulp may respond normal to testing.', 'role': 'assistant'}]