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: Surgery
According to Cawood and Howell, a depression with cup shaped surface of edentulous atrophic maxilla is classified as 
Select and explain. 
A. Class III, B. Class IV, C. Class V, D. Class VI
D: Class VI
Answer: D: Class VI 
Explanation: None