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
Retention of inlay is increased by 
Select and explain. 
A. Increased axial length of preparation, B. flat pulpal walls, C. Rounded internal line angles, D. all of the above
A: Increased axial length of preparation
Answer: A: Increased axial length of preparation 
Explanation: None