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 walls of full gold crown preparation should: 
Select and explain. 
A. Be parallel, B. Angle of convergence 5°, C. Angle of divergence 5°, D. Roughened to increase retention
A: Be parallel
Answer: A: Be parallel 
Explanation: None