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': 'Which of the following device works on the principle of electric conductance? \nSelect and explain. \nA. DIAGNOdent, B. QLF, C. CarieScan Pro, D. None of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Devices using electric conductance are:\n\nVanguard electronic caries detector\xa0\nCaries meter\nModified electrochemical impedance spectroscopy\nElectrical impedance tomography', 'role': 'assistant'}]