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
The causative organism of syphilis is: 
Select and explain. 
A. Borrelia burgdorferi, B. Chlamydia trachomatis, C. Leptospira interrogans, D. Treponema pallidum
D: Treponema pallidum
Answer: D: Treponema pallidum 
Explanation: None