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': 'All are true about cystic hygroma, except \nSelect and explain. \nA. Pulsatile, B. May cause respiratory obstruction, C. Common in neck, D. Present in birth', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]