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
Fins in casting are seen 
Select and explain. 
A. Round margin in casting, B. Too Long heating, C. Air bubbles on wax, D. Cracking of investment
D: Cracking of investment
Answer: D: Cracking of investment 
Explanation: None