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
Total arch length reduced due to mesial migration of teeth? 
Select and explain. 
A. 1 cm, B. 3 cm, C. 0.5 cm, D. 0.15 cm
C: 0.5 cm
Answer: C: 0.5 cm 
Explanation: None