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': '1 part per million fluoride is: \nSelect and explain. \nA. 1 mg in 10 L of water, B. 1 mg in 1 L of water, C. 10 mg in 1 L of water, D. 100 mg in 10 L of water', 'role': 'user'}, {'content': 'Answer: B \nExplanation: ppm (or ppmm) is used to measure the concentration of a contaminant in soils and sediments. In that case,\xa01 ppm equals 1 mg of substance per liter of solid (mg/liter).', 'role': 'assistant'}]