Dr. Clark is interested in buying Darwin a new type of treat. She makes her choice based on the popularity of treats from the Petco Treat Bar. Her hypothesis is that dog owners will favor one type of treat over another. Therefore, she goes to Petco and observes how much (in kilograms) the patrons purchase of one of four types of treats: sandwich creme, pumpkin & spice, spring flowers, and cheddar cheese. Who is the population (units at the construct level) in Dr. Clark's study?

Group of answer choices

dogs

pet owners

dog treats

amount of treats in kilograms