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
A purine which is found in saliva is: 
Select and explain. 
A. Uric acid, B. Thymine, C. Adenosine, D. Hypolithinium
C: Adenosine
Answer: C: Adenosine 
Explanation: None