This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: DNB 2018, Subject name: Physiology
[{'content': '68-years-old man weighing 60 kg has plasma creatinine 3mg/dL. What will be creatinine clearance? \nSelect and explain. \nA. 10, B. 20, C. 30, D. 40', 'role': 'user'}, {'content': 'Answer: B \nExplanation: By Cockcroft & Gault formula Factors influencing 1. Body wt. - Assumed to be d/o muscle mass - Muscle - creatine - creatinine 2. Age - with advancing age, number of functional nephrons decrease Cockcroft & gault formula unreliable in: - 1. Obesity 2. Pregnancy', 'role': 'assistant'}]