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
Seibert’s class II defect is: 
Select and explain. 
A. Faciolingual loss of tissues with normal ridge height, B. Normal ridge width with loss of ridge height, C. Loss of height and width, D. None of the above
B: Normal ridge width with loss of ridge height
Answer: B: Normal ridge width with loss of ridge height 
Explanation: Seibert’s Classification
Class 0 defects - No defect.
Class I defects - Faciolingual loss of tissue width with normal ridge height.
Class II defects - Loss of ridge height with normal ridge width.
Class III defects - A combination of loss in both dimensions.