Which sexually transmitted infection (STI) can be successfully treated with antibiotics ? A Human papilloma virus (HPV)
B syphilis
C hepatitis c
D genital herpes

Syphilis can be successfully treated with antibiotics.

Antibiotics target diseases and infections that are caused by bacteria so a sexually transmitted infection that is caused by bacteria can be treated with antibiotics.

The only infection caused by bacteria in the options is Syphilis.

Other STIs that can be treated by antibiotics include:

The other infections in the question are caused by viruses which are tougher to treat and so cannot be treated by antibiotics.

In conclusion, antibiotics are able to treat infections caused by bacteria and because syphilis is one, it can be treated by antibiotics.

For more information on STIs check:

I know this is from a long time ago and you already have a great answer, but:

B syphilis

     Syphilis is a bacteria infection, and antibiotics target diseases + infections caused by bacteria, so the answer will have to be B as none of the other options are caused from bacteria.