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
What is the established vertical dimension freeway space 
in millimeters? 
Select and explain. 
A. 6-May, B. 3-Jan, C. 4-Feb, D. 8-Jun
C: 4-Feb
Answer: C: 4-Feb 
Explanation: None