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: Pharmacology
[{'content': 'A middle aged old man, with chronic renal failure is diagnosed to have sputum positive pulmonary tuberculosis. His creatinine clearance is 25m1/min. All of the following drugs need modification in doses except- \nSelect and explain. \nA. Isoniazid, B. Streptomycin, C. Rifampicin, D. Ethambutol', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Rifampicin", 'role': 'assistant'}]