Why are cells described as the "building blocks" of all living things?

Question 3 options:

Cells are always stacked in rows, like bricks, to build the parts of living things.

A cell is the smallest part of a living thing that can function on its own.

They are found in everything living things need, including water and food.

A cell is the smallest part of the air living things need to breathe

A cell is the smallest part of a living thing that can function on its own.