This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oncology, Subject name: Medicine
Which of the following tests is not used in the diagnosis of insulinoma - 
Select and explain. 
A. Fasting blood glucose, B. Xylose test, C. C- peptide levels, D. Insulin/Glucose Ratio
B: Xylose test
Answer: B: Xylose test 
Explanation: <img src=" /> Ref Harrison 20th edition pg 567