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: Gynaecology & Obstetrics
[{'content': 'Most common ovarian tumour in pregnancy is: \nSelect and explain. \nA. Mucinous cyst adenoma, B. Dermoid cyst, C. Metastasis, D. Dysgerminoma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]