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': 'A patient manifests systemic symptoms of pallor and unconsciousness following local anesthesia. The patient is experiencing: \nSelect and explain. \nA. CNS depression, B. Syncope, C. Tonic reaction to local anesthesia, D. Allergic response', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]