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
Softening heat treatment of alloy increases: 
Select and explain. 
A. Tensile strength, B. Proportional limit, C. Ductility, D. Hardness
C: Ductility
Answer: C: Ductility 
Explanation: None