This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Histo Pathology, Subject name: Pathology
[{'content': 'NaF is used in which color cap vacutainer? \nSelect and explain. \nA. Grey, B. Yellow, C. Red, D. Blue', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. GreyHemogard stopperTube contentDetermination Serum separator tube (SST)All biochemistry not mentioned elsewhere (1 tube), microbiology (1 tube)HeparinChromosome studies, lead, amino acids, troponinFluoride/ oxalateGlucoseEDTAFull blood count (FBC) and ESR, C3/C4,Hemoglobin A1c, Homocysteine, ACTHPlain (no additive)LDH, Ca, drugs (phenytoin, theophylline, lithium), endocrine testing (except thyroid) Sodim citrateCoagulation testing, PT, INR, APTT, D-dimer, etc.ESRWestergren sedimentation rate; requires full draw', 'role': 'assistant'}]