This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Physiology
Saliva is 
Select and explain. 
A. Hypeonic, B. Hypotonic, C. Isotonic, D. At first hypeonic, then isotonic
B: Hypotonic
Answer: B: Hypotonic 
Explanation: Saliva has a pH normal range of 6.2-7.6 with 6.7 being the average pH. Resting pH of mouth does not fall below 6.3. In the oral cavity, the pH is maintained near neutrality (6.7-7.3) by saliva. The saliva contributes to maintenance of the pH by two mechanisms Ref: guyton and hall textbook of medical physiology 12 edition page number:400,401,402