The purpose of the immune system is to?
a. give you diarrhea.
b. make your nose run.
c. fight off sickness.
d. germs invade your body.

Option c. Fight off sickness by attacking pathogens that your body comes into contact with.

Explanation:

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme