$A$ sexually transmitted disease, symptomatized by the development of ulcers on the genitals, is caused by the infection of

Syphilis is an infectious bacterial disease caused by $Treponema\ pallidum$ with $3$ stages:
$(A)$ Infectious painless ulcers on the genitals $\quad(i)$ First
$(B)$ Blindness, heart trouble, aortic impairment $\quad(ii)$ Second
$(C)$ Skin lesions, hair loss, swollen joints $\quad(iii)$ Third
Which of the following is the correct match between the symptoms and stage?

How many of the following diseases are included in $STDs$?
Gonorrhoea,Syphilis,Genital herpes,Chlamydiasis,Genital warts,Cancer,Trichomoniasis,Hepatitis-$B$,$AIDS$,Typhoid,Malaria

Which of the following cannot protect the user from contracting $AIDS$?

Which of the following sexually transmitted diseases is caused by a protozoan?

Which of the following principles are used to prevent $STD$ infection?
$(i)$ Avoid sex with unknown partners
$(ii)$ Use condoms during coitus
$(iii)$ Blood transfusion
$(iv)$ All of these