Which sentence represents a relationship between the number of visits
to the gym that Denise makes and her total gym cost that results in a
line with zero slope?
A. Denise pays an annual fee for an all-inclusive gym membership.
B. Denise pays an annual fee for a gym membership and $15 each time she chooses to take a spin class.
C. Denise pays $50 per month for 10 monthly visits, then $3 for each additional visit.
D.Denise pays $6 each time she visits the gym.