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
Tempering of steel cause 
Select and explain. 
A. increases its toughness, B. increases hardness, C. increases ductility, D. decreases its toughness
A: increases its toughness
Answer: A: increases its toughness 
Explanation: None