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
The retention for class 5 restoration are placed: 
Select and explain. 
A. In mesial and distal areas, B. Occlusal and gingival area, C. In all except the axial wall, D. At expense of axial wall
B: Occlusal and gingival area
Answer: B: Occlusal and gingival area 
Explanation: None