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
Andrew's 5th key of occlusion is 
Select and explain. 
A. Curve of spee, B. Rotation absent, C. Tight contacts, D. Bolton's ration
C: Tight contacts
Answer: C: Tight contacts 
Explanation: None