'Syphilis' is a sexually transmitted disease caused by

Which of the following causative agents of $STDs$ can cross the placenta?

The sexually transmitted disease that can affect both the male and the female genitals and may damage the eyes of babies born of infected mothers is

Which of the following is an $STD$?

The 'symptomless' period or latent period in case of syphilis may last for

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