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': 'Rate of activation with slow expansion is \nSelect and explain. \nA. 1 mm per day, B. 1 mm for 3 days, C. 1 mm for a month, D. 1 mm per week', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]