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': 'he brilliantly transilluminant tumour in the neck may be - \nSelect and explain. \nA. Branchial cyst, B. Thyroglossal cyst, C. Sternomastoid tumour, D. Cystic hygroma', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Cystic hygroma", 'role': 'assistant'}]