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': 'Sprue should ideally be made of \nSelect and explain. \nA. Inlay wax, B. plastic rod, C. Hollow plastic, D. hollow metal', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]