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: Physiology
To preserve blood for transfusion later: 
Select and explain. 
A. Dilute with equal volume of 0.9% saline, B. Add solution of sodium citrate, C. Add solution of calcium chloride, D. Add fibrinogen
B: Add solution of sodium citrate
Answer: B: Add solution of sodium citrate 
Explanation: None