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
Indirect retainers are most effective when: 
Select and explain. 
A. They rest bilaterally on cingulum of canines, B. Rest on mesial surface of premolars with extensions on to canines, C. They rest on incisal edges of canines, D. Rest on incisal edges of lateral incisors with extensions on to central incisiors
B: Rest on mesial surface of premolars with extensions on to canines
Answer: B: Rest on mesial surface of premolars with extensions on to canines 
Explanation: None