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
According to the type of movement of the anchorage unit, it can be classified as all except 
Select and explain. 
A. Simple, B. Compound, C. Reciprocal, D. Stationary
B: Compound
Answer: B: Compound 
Explanation: None