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: Medicine
[{'content': 'The completeness of a 24-hour urine collection is best assessed by the simultaneous measurement of urinary - \nSelect and explain. \nA. Volume, B. Urea, C. Creatinine, D. pH', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]