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
A problem with a porcelain jacket is it: 
Select and explain. 
A. Is not color stable, B. Is very brittle, C. Has a very high compression strength, D. Is irritating to the gingiva
B: Is very brittle
Answer: B: Is very brittle 
Explanation: None