This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
what is the anticoagulant of choice in electrolyte estimation ? 
Select and explain. 
A. lithium heparin, B. trisodium citrate, C. EDTA, D. all of the above
A: lithium heparin
Answer: A: lithium heparin 
Explanation: (Anticoagulant) : * Is a substance that prevents blood from coagulation or clotting. * The most common anticoagulants used in hematology are: 1. EDTA: Ethylen Diamine Tetraacetic acid -CBC , RBC MORPHOLOGY 2. Sodium citrate - FOR COAGULATION STUDIES 3. Heparine -ABG (ELECTROLYTES), IMMUNOPHENOTYPING ,LEUKOCYTE FUNCTION DEFECT , OSMOTIC FRAGILITY TEST REF : ROBBINS 10TH ED