A(n) is a chemical substance used to treat, prevent, or diagnose a disease or alter one or more functions of the body.
stimulant
antibiotic
drug
narcotic

You did not show us the image of the burger, but i shall try to answer as best i can.  when purchasing food, always consider the ingredients as well as the person who prepared it. consider if they were hygienic people or not, in case the burger was infected with bacteria. no mortal should place an infected burger into their mouth.   

Your answer is going to be c.