$STDs$ are also called

Which of the following principles should be followed to stay free from Sexually Transmitted Infections $(STIs)$?

What measures should be taken to avoid the transmission of $STD$s?
$I$. Avoid sex with unknown partners
$II$. Avoid sex with multiple partners
$III$. Use protection during sex
$IV$. Avoid sharing needles

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?

Which pathogen is responsible for syphilis?

The appearance of chancre and rashes all over the body are the symptoms of