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
Rate of activation with slow expansion is 
Select and explain. 
A. 1 mm per day, B. 1 mm for 3 days, C. 1 mm for a month, D. 1 mm per week
D: 1 mm per week
Answer: D: 1 mm per week 
Explanation: None