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: Social & Preventive Medicine
[{'content': 'Most reliable test for screening of diabetes mellitus \nSelect and explain. \nA. Random blood sugar, B. Urine sugar, C. Glucose tolerance test, D. Fasting blood sugar', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]