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: Pathology
[{'content': "In Wintrobe's method for ESR, anticoagulant used is -a)  Double oxalate b) EDTAc)  Trisodium citrated) Citrate \nSelect and explain. \nA. ac, B. a, C. ab, D. bc", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]