This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
which is true about WIDAL REACTION 
Select and explain. 
A. Antibody to H antigen appears first and persist, B. Antibody to O antigen appears first and persist, C. Antibodies to H and O antigen appears simultaneously, D. none of the above.
A: Antibody to H antigen appears first and persist
Answer: A: Antibody to H antigen appears first and persist 
Explanation: None