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 and spines on the casting is seen due to 
Select and explain. 
A. Prolonged heating, B. Rapid heating rate, C. Water film contamination, D. Too high pressure during casting
B: Rapid heating rate
Answer: B: Rapid heating rate 
Explanation: None