I need help please
which one is a function rule

A) Jade pushes the Dr. Pepper button on a soda machine and receives a can of Dr. Pepper. She then pushes the same Dr. Pepper button again and receives a can of Sierra Mist this time.

B)Gage weighs 163 pounds. When Gage's parents measured his height, his mom says he is 63 inches tall while his dad says Gage is 72 inches tall.

C) Aaliyah earns $25 for each hour she babysits.

D)The size of a case and the number of balls in the case.

which one is it?