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 soft, cystic, fluctuant swelling in a child's neck which\nis brilliantly translucent is most likely \nSelect and explain. \nA. Sternornastoid tumour, B. Cystic hygroma, C. Branchial cyst, D. Cold abscess", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]