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

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

Chancroid is a sexually transmitted disease caused by:

Syphilis is a sexually transmitted disease caused by which of the following?

Which of the following can be complications resulting from $STDs$ without timely detection and treatment?
$A.$ Pelvic inflammatory disease $(PID)$
$B.$ Stillbirths
$C.$ Infertility or even cancer of the reproductive tract
$D.$ Ectopic pregnancies

Which of the following is correct regarding genital herpes?