This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: miscellaneous, Subject name: Pathology
Blood when stored at 4degC can be kept for 
Select and explain. 
A. 7 days, B. 14 days, C. 21 days, D. 28 days
C: 21 days
Answer: C: 21 days 
Explanation: When blood is stored at 2-6 degC, glycolysis is reduced but does not stop. Giycosis results in the production of lactate, with a subsequent decrease in pH. Whole blood collected in CPD has a pH7.20 on day 0 and 6.84 on day 21. Preservative solutions provide the buffering capability to minimize pH changes and optimize the storage period. Ref: Medscape