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: Dental
[{'content': 'A pregnant lady uses fluoridated drinking water. All of the following are true regarding exposure of the foetus to fluoride except: \nSelect and explain. \nA. The placenta acts as a regulator and reduces the concentration of fluorides reaching the foetus, B. The placenta acts as a regulator and increases the concentration of fluorides reaching the foetus, C. Both, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: There are different views regarding the passage of fluoride across the placenta.\nSome authors have said that placenta acts as a complete barrier to fluoride, others have said that it is only partial.\xa0\nSome have said that the placenta only acts as a barrier when there is a sudden increase in the maternal plasma fluoride level.\n\nEssentials of preventive and community dentistry\xa0\nSoben Peter\xa0\n5th edition', 'role': 'assistant'}]