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: Surgery
A condition of the mouth which increases the caries activity in the oral cavity is 
Select and explain. 
A. Xerostomia, B. Fissured tongue, C. Hairy tongue, D. Watery saliva
A: Xerostomia
Answer: A: Xerostomia 
Explanation: None