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
[{'content': 'The longer and more parallel opposing walls of a cast restoration \nSelect and explain. \nA. The greater the retention, B. The greater the resistance, C. The greater the compressive strength, D. The greater the tensile strength', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The gingival-to-occlusal divergence of these preparation walls may\xa0range from 2 to 5 degrees per wall from the line of draw. If the\xa0vertical walls are unusually short, a maximum of 2 degrees occlusal\xa0divergence is desirable to increase retention potential. As the\xa0occlusogingival height increases, the occlusal divergence should\xa0increase because lengthy preparations with minimal divergence\xa0(more parallel) may present diiculties during the seating and\xa0withdrawal of the restoration.\nSturdevant Operative Dentistry 7th edition page. e97', 'role': 'assistant'}]