Bacteria in your intestines are an example of mutualism if they
a. make you sick. b. have no effect on you. c. are destroyed by digestive juices. d. you break down food.

if they help you break down food

Explanation:

Mutualism is a biological relationship between TWO or more organisms of different species (inter-specie) in which one or more benefits.

A good example is bacteria in the human intestine that helps to break down cellulose contained in food, thus benefitting humans.

the denominator has a very specific role.