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
[{'content': 'Which of the following tests is not used in the diagnosis of insulinoma - \nSelect and explain. \nA. Fasting blood glucose, B. Xylose test, C. C- peptide levels, D. Insulin/Glucose Ratio', 'role': 'user'}, {'content': 'Answer: B \nExplanation: <img src=" /> Ref Harrison 20th edition pg 567', 'role': 'assistant'}]