Since It Has Been Medically Proven That Watching Fish Reduces

Since it has been medically proven that watching fish reduces anxiety,many physicians' offices have installed large fish tanks in their waiting rooms.There has been a tank in Dr.McKinnon's office for six years.Yesterday,his receptionist went to the pet store and purchased three replacement goldfish after a patient commented on the fact there were no living fish in the aquarium.
-Refer to Goldfish.Which of the following statements correctly describes the buying centre?

A) The patient was an initiator and an influencer.
B) The receptionist was a gatekeeper.
C) The patient was the decider.
D) The patient was the gatekeeper.