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: Surgery
[{'content': 'Following extraction of the impacted mandibular canine, which involved the use of micromotor, the patient developed severe pain and ecchymosis as seen in the color plate. What can be the cause? \nSelect and explain. \nA. Post surgical ecchymosis, B. Herpes labialis activation, C. Air emphysema, D. Sodium hypochlorite injection', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The information provided in the question and image leads to diagnosis of post surgical ecchymosis. The main symptom of emphysema is a crepitus of the swollen tissues', 'role': 'assistant'}]