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': 'Sub surface porosity can be decreased by: \nSelect and explain. \nA. Decreasing the sprue length, B. Decreasing the sprue thickness, C. Increasing the melting temperature, D. Increasing the mould temperature', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]