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
Incomplete casting can be due to: 
Select and explain. 
A. Insufficient venting., B. Inadequate or too small spreu., C. Low casting pressure., D. All of the above.
D: All of the above.
Answer: D: All of the above. 
Explanation: Reasons for incomplete castings:

Insufficient venting
Inadequate sprue (too small sprue)
Insufficient alloy used
Alloy not sufficiently molten or fluid
Mold is not heated to casting temperature
Premature solidification of alloy
Low casting pressure