plz provide the explanation of this qn no.9 ans given in book option a. which I feel is wrong. it should be option d right?

Dear student,
Please find below the answer:

The correct option is (d).

A Sexually transmitted disease (STD) is a disease that gets transferred from one person to another through sexual contact. Some common sexually transmitted diseases are herpes, HIV-AIDS, syphilis, gonorrhea, etc.

Since a 5-year-old is unlikely to indulge in any sexual act, his chances of contracting an STD are very little.

Hope this clears your doubt.
Regards.