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: Surgery
[{'content': 'Blood loss during major surgery is best estimated by: \nSelect and explain. \nA. Visual assessment, B. Suction bottles, C. Transesophageal USG Doppler, D. Cardiac output by thermodilution', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Measurement of blood loss during surgery (Gravimetric Method)\n\nBlood loss during operation is measured by: Weighing the swabs after use and subtracting the dry weight and fluid used + volume of blood collected in suction bottles (after subtracting irrigating fluid)', 'role': 'assistant'}]