This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
All the following strains of proteus are used in Weil-Felix reaction Except 
Select and explain. 
A. OX 2, B. OX 19, C. OX K, D. OX O
D: OX O
Answer: D: OX O 
Explanation: Alkali stable polysaccharide, a surface antigen is seen in some rickettsiae and some strains of Proteus bacilli. This is the basis for the Weil-Felix reaction used for the diagnosis of rickettsial infections by the demonstration of agglutinins to Proteus strains OX 19, OX 2, and OX K.Ref: Ananthanarayan; 7th edition; Page no: 413