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': 'Mercury intoxication in dental office mainly results from: \nSelect and explain. \nA. Direct contact with the mercury, B. Inhalation of mercury vapours, C. Ingestion of mercury, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]