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: Social & Preventive Medicine
[{'content': 'Lead concentration in bone indicates: \nSelect and explain. \nA. Recent exposure, B. Cumulative exposure, C. Both of the above, D. None of the above', 'role': 'user'}, {'content': "Answer: B \nExplanation: The absorbed lead, both inhaled and ingested, is transpoed to the blood stream where a rapid equilibrium is established between plasma and red cells in a propoion of 1:16. From the blood stream, the lead is delivered to all organs, especially bones which may retain around 90% of the body's lead content. Therefore, while the blood lead concentration reflects the recent exposure, bone lead concentration reflects the cumulative exposure. Ref :", 'role': 'assistant'}]