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
Most reliable test for screening of diabetes mellitus 
Select and explain. 
A. Random blood sugar, B. Urine sugar, C. Glucose tolerance test, D. Fasting blood sugar
D: Fasting blood sugar
Answer: D: Fasting blood sugar 
Explanation: None