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
Function of WHO collaborating centers: 
Select and explain. 
A. Collection, collation and dissemination of information, B. Functioning and forming new guidelines/definitions for diseases, C. Contact with grass root workers, D. Collaborate information mainly
A: Collection, collation and dissemination of information
Answer: A: Collection, collation and dissemination of information 
Explanation: None