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 IV 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
D: None of the above
Answer: D: None of the above 
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.