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
A man with very high fever shows strongly positive agglutination test with OXK antigen. The most likely diagnosis is- 
Select and explain. 
A. Tsutsugamushi fever, B. Trench fever, C. Undulent fever, D. Relapsing fever
A: Tsutsugamushi fever
Answer: A: Tsutsugamushi fever 
Explanation: None