Question

which phrase accurately characterizes sexually transmitted infections (stis)?
are caused by bacteria, viruses, or parasites
always cause visible symptoms
are rarely transmitted by sexual contact
can be contracted only by women

Explanation:

Sexually transmitted infections (STIs) can be caused by bacteria (e.g., chlamydia, gonorrhea), viruses (e.g., HIV, herpes simplex virus), or parasites (e.g., trichomoniasis). Many STIs may not show visible symptoms (so "always cause visible symptoms" is wrong). STIs are mainly transmitted by sexual contact (so "rarely transmitted by sexual contact" is wrong). Both men and women can contract STIs (so "can be contracted only by women" is wrong).

Answer:

are caused by bacteria, viruses, or parasites