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
Mouth preparation for removable cast partial denture include 
Select and explain. 
A. Periodontal preparation only, B. Oral surgical preparation only, C. Abutment tooth preparation only, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: None