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
To increase resistance form of an excessively tapered preparation: 
Select and explain. 
A. Reduce height of preparation to shorten arc of rotation, B. Increase cervical reduction to taper, C. Add groove, D. Use adhesive cement
C: Add groove
Answer: C: Add groove 
Explanation: None