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
[{'content': 'Incomplete casting can be due to: \nSelect and explain. \nA. Insufficient venting., B. Inadequate or too small spreu., C. Low casting pressure., D. All of the above.', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Reasons for incomplete castings:\n\nInsufficient venting\nInadequate sprue (too small sprue)\nInsufficient alloy used\nAlloy not sufficiently molten or fluid\nMold is not heated to casting temperature\nPremature solidification of alloy\nLow casting pressure', 'role': 'assistant'}]