The table below shows the number of cups of food Trey's cat ate over time. 
 Number of cups: 3, 4, 9, 12, 15
 number of days: 4, 8, 12, 16, 20
 Which statement gives a unit rate?
 A: For every day, Trey's cat ate 1.5 cups
 B: For every cup, Trey's cat ate for 1.5 days
 C: For every cup, Trey's cat ate for 0.75 of a day
 D: For every day, Trey's cat ate 0.75 of a cup