You are presented with the quiz "Scraping oneself on an object that is what, may cause an invasion of the body by bacteria?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "scraping oneself on a contaminated object may cause infection" and "an infection is an invasion of the body by bacteria". 

So, what's the best answer to the question?


 

        contaminated   