The correct answer is realistic!
A. The school bus drove over the hill, its lumbering yellow form full of raucous students.
Virus is actually just a piece or strand of genetic information usually DNA or RNA which can be single or double stranded.
Viruses are everywhere from our surroundings to the very food we eat. We ingest, inhale and talk in millions of viruses every second. Pretty much all life on Earth has some kind of virus designed specifically to infect in including bacteria and even other viruses. Viruses are tiny very tiny you can visibly see them if fact they are so small that if bacteria had eyes even they wouldn't be able to see all of them.