C  

Potassium oxalate acts as the anticoagulant while sodium fluoride inhibits glycolysis, making the potassium-oxalate/sodium-fluoride (“fluoride oxalate”) tube the standard for transporting blood samples for glucose estimation from primary health centres. This combination preserves glucose far better than EDTA, heparin or oxalate alone [Waring et al., 2007, PMID 17596547].