Checking each sentence, we have:
A. The sentence relates the total price for some packs of notebooks: four packs are $20 and five packs are $25, so in this case we have a function relating the total cost and the number of packs.
B. The sentence relates the total price charged for a certain number of hours of babysitting, and the price increases as the number of hours increases, so in this case we have a function.
C. The sentence relates the total distance and the time spent driving, and an increase in the time causes an increase in the distance, so we have a function.
D. In this case we can see that the same number of gumballs (six) has two different times (two hours and three hours), so this case do not represent a function.
So the answer is D.
