This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urinary tract, Subject name: Pathology
[{'content': 'Uremia occurs when total GFR is reduced by- \nSelect and explain. \nA. 25%, B. 50%, C. 60%, D. 80%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: There is no specific time for the onset of uremia for people with progressive loss of kidney function. People with kidney function below 50% (i.e. a glomerular filtration rate between 50 and 60 mL) and over 30 years of age may have uremia to a degree. Ref: Wikipedia', 'role': 'assistant'}]