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
Cast metal is protected from localized porosity by 
Select and explain. 
A. Bevelling, B. Adding reservior sprue., C. Tunneling, D. Investment
B: Adding reservior sprue.
Answer: B: Adding reservior sprue. 
Explanation: Proper planning if sprue location and reservior are essential to prevent porosity in cast alloys.