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
In order to prevent dehydration of periosteal surface of the flap, it should be irrigated frequently with: 
Select and explain. 
A. Water, B. CHX, C. Saline, D. All of the above
C: Saline
Answer: C: Saline 
Explanation: To prevent dehydration of periosteal surface of the ﬂap, it should be irrigated frequently with saline (0.9% NaCl), and not with water, as it is hypotonic.