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: Medicine
Urinary D-Xylose test is used for the the study of: 
Select and explain. 
A. Proximal small bowel mucosal function, B. Distal small bowel mucosal function, C. Proximal small bowel serosal function, D. Distal small bowel serosal function
A: Proximal small bowel mucosal function
Answer: A: Proximal small bowel mucosal function 
Explanation: The urinary D-xylose test: Used for carbohydrate absorption Assesses proximal small-intestinal mucosal function. Ref: Harrison, E-18, P-2467.