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
Rough surface on casting occurs due to 
Select and explain. 
A. Investment breakdown., B. Air bubbles on wax., C. Weak surface of investment., D. All of the above.
D: All of the above.
Answer: D: All of the above. 
Explanation: None