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
Proteus antigen cross-react with? 
Select and explain. 
A. Klebsiella, B. Rickettsiae, C. Chlamydiae, D. E.coli
B: Rickettsiae
Answer: B: Rickettsiae 
Explanation: None