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
Blood loss during major surgery is best estimated by: 
Select and explain. 
A. Visual assessment, B. Suction bottles, C. Transesophageal USG Doppler, D. Cardiac output by thermodilution
B: Suction bottles
Answer: B: Suction bottles 
Explanation: Measurement of blood loss during surgery (Gravimetric Method)

Blood 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)