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
Sub surface porosity can be decreased by: 
Select and explain. 
A. Decreasing the sprue length, B. Decreasing the sprue thickness, C. Increasing the melting temperature, D. Increasing the mould temperature
B: Decreasing the sprue thickness
Answer: B: Decreasing the sprue thickness 
Explanation: None