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': 'Maternal sources account for what percentage of fetal thyroxine at term \nSelect and explain. \nA. 10%, B. 30%, C. 50%, D. 70%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 30% of fetal thyroxine at term is derived from mother.', 'role': 'assistant'}]