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: Physiology
[{'content': 'Which of the following does not changes in the old age \nSelect and explain. \nA. GFR, B. Glucose tolerance, C. Haematocrit, D. Blood pressure', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]