This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
[{'content': 'What is the GFR (mL/min per 1.73m2) of a patient who is in G4 category of chronic kidney disease \nSelect and explain. \nA. 60-89, B. 30 - 59, C. 15 - 29, D. < 15', 'role': 'user'}, {'content': "Answer: C \nExplanation: Reference: Harrison's Principles of Internal Medicine; 20th edition; Chapter 335 Chronic Kidney Disease , pg 2112", 'role': 'assistant'}]