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
The longer and more parallel opposing walls of a cast restoration 
Select and explain. 
A. The greater the retention, B. The greater the resistance, C. The greater the compressive strength, D. The greater the tensile strength
A: The greater the retention
Answer: A: The greater the retention 
Explanation: The gingival-to-occlusal divergence of these preparation walls may range from 2 to 5 degrees per wall from the line of draw. If the vertical walls are unusually short, a maximum of 2 degrees occlusal divergence is desirable to increase retention potential. As the occlusogingival height increases, the occlusal divergence should increase because lengthy preparations with minimal divergence (more parallel) may present diiculties during the seating and withdrawal of the restoration.
Sturdevant Operative Dentistry 7th edition page. e97