This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Medicine
Which one of the following laboratory tests differentiates leukemoid reaction from chronic myeloid leukemia? 
Select and explain. 
A. LAP (leukocyte alkaline phosphatase), B. LCA (leukocyte common antigen), C. MPO (myelo-peroxidase), D. TRAP (tarate resistant alkaline phosphatase)
A: LAP (leukocyte alkaline phosphatase)
Answer: A: LAP (leukocyte alkaline phosphatase) 
Explanation: <p>Leucocyte alkaline phosphate score in the cytoplasm of mature neutrophils in leukamoid reaction is characteristically high & ia very useful to distinguish it from CML. Leukaemoid reaction is defined as reactive excessive leucocytosis in response to infections,intoxication ,malignant disease ,& in severe hemmorhage & hemolysis.So mature neutrophils will be more resulting in elevated LAP.But in CML,mature neutrophils will be reduced resulting in low LAP score. </p><p>Reference :Harsh mohan textbook of pathology sixth edition pg no 353.</p>