This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infections of the genital tract, Subject name: Gynaecology & Obstetrics
A 19-year-old girl with painless ulcer in labia majora with rolled out margin : 
Select and explain. 
A. Treponema pallidum, B. Chlamydia, C. Gonorrhoea, D. Herpes genital ulcer disease
A: Treponema pallidum
Answer: A: Treponema pallidum 
Explanation: syphilis Caused by Treponema pallidum classic lesion designated as chancre appears in 9-90 days from first exposure The macular lesions become papular and then ulcerates.The ulcer is painless and firm,with a punched out base,and rolled edges. SHAW'S TEXTBOOK OF GYNAECOLOGY,Pg no:142,15th edition