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': 'Cast metal is protected from localized porosity by \nSelect and explain. \nA. Bevelling, B. Adding reservior sprue., C. Tunneling, D. Investment', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Proper planning if sprue location and reservior are essential to prevent porosity in cast alloys.', 'role': 'assistant'}]