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': 'Earliest tumour to appear after birth is- \nSelect and explain. \nA. Sternomastoid tumour, B. Cystic hygroma, C. Branchial cyst, D. Lymphoma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 50 to 65% of cystic hygroma are present at birth.', 'role': 'assistant'}]