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[{'content': 'Local anaesthetic injections\nA fail, usually because the anaesthetic solution is out of date \nB followed by collapse is usually because of allergy to one of the constituents \nC followed by trismus after the effect of inferior dental local anaesthetic block has subsided usually indicates trauma in the region of the medial pterygoid muscle and/or a haematoma \nD except for local infiltrations should be avoided in patients with haemophilia \nSelect and explain. \nA. AB is true and CD are false, B. AB are false and CD are true, C. AC are true and BD are false, D. AC are false an BD are true', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]