This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glomerular Filtration, Renal Blood Flow, and Their Control, Subject name: Physiology
[{'content': 'The most sensitive index for renal tubular function is : \nSelect and explain. \nA. Specific gravity of urine, B. Blood urea, C. GFR, D. Creatinine clearance', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' specific gravity of urineThe main function of renal tubules is concentration of urine and this can be measured by the specific gravity of urine.", 'role': 'assistant'}]