Phlebotomy Technician Practice Exam (NCPT/CPT)

Green top tubes are typically used for collecting blood specimens for electrolyte testing. Of the options listed, sodium citrate is commonly used for coagulation testing, EDTA is used for complete blood counts, and no additive tubes are used for other types of testing. Lithium heparin, on the other hand, is the most commonly used additive for collecting specimens for electrolyte testing, making it the best option for the green top tubes. It prevents the clotting process and allows for accurate testing of electrolyte levels. Therefore, option C is the correct answer.