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
If during an application of an orthodontic force, the level declines to zero between activations then the force duration is classified as: 
Select and explain. 
A. Continuous force, B. Interrupted force, C. Intermittent force, D. Differential force
B: Interrupted force
Answer: B: Interrupted force 
Explanation: None