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 cystic, painless swelling along the upper border of sternocleidomastoid muscle is most likely to be: March 2013 (b) \nSelect and explain. \nA. Thyroglossal cyst, B. Branchial cyst, C. Cystic hygroma, D. Branchial fistula', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B i.e. Branchial cyst', 'role': 'assistant'}]