Which is the best unit?

Scroll down to find the best unit.
The weight of a five year-old
The amount of liquid a pot can hold
The weight of a pencil
The height of a building
The distance between two cities
The weight of a car
The amount of water a small cup can hold
The length of a driveway
The amount of liquid in a bowl of cereal
The weight of a notebook
The length of a classroom
The length of a large forest
The amount of liquid in a pitcher
The weight of a flower
The weight of a refrigerator