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': 'True about cystic hygroma -a) Congenital sequestration of lymphaticsb) Resolves spontaneouly by 5 year of agec) Common in upper 1/3rd of lateral neckd) Surgery is the treatment of choice \nSelect and explain. \nA. b, B. ad, C. ac, D. ab', 'role': 'user'}, {'content': 'Answer: B \nExplanation: "Bailey writes that spontaneous regression may occur in cystic hygroma but I am not sure whether it occurs by 5 yrs of age".', 'role': 'assistant'}]