This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sexually Transmitted Disease in the Female, Subject name: Gynaecology & Obstetrics
A female presents with 3 cms painless ulcer with raised edges on Labia majra M/c cause is: 
Select and explain. 
A. Syphilis, B. Gonorrhea, C. Herpes, D. Chlamydia
A: Syphilis
Answer: A: Syphilis 
Explanation: Ans. is a, i.e. SyphilisRef: Williams Gynae 3rd/ed, p56"With pregnancy syphilis, the halltnark lesion is the chancre, in which spirochactes are abundant classically, it is an isolated non tender ulcer with raised sounded borders and an uninfected base." - Ref: Williams Gynae 3rd/ed, p56