* A rock: Rocks are inanimate objects, lacking the complex organization and biological processes of cells.

* A water molecule: Water molecules are simple chemical compounds, not complex structures like cells.

* A virus: While viruses can infect cells and replicate inside them, they are not considered living organisms. They lack the ability to perform many essential biological functions on their own, such as generating energy or synthesizing proteins.

* A computer: Computers are machines, designed and built by humans, and do not possess the characteristics of living cells.

* A cloud: Clouds are formed from water droplets or ice crystals, and are not biological entities.

Essentially, anything that does not have the following characteristics of a cell is a non-example:

* Organized structure: Cells have a distinct internal structure with specialized components like a nucleus, cytoplasm, and membrane.

* Metabolism: Cells carry out chemical reactions to obtain energy and create the materials they need.

* Growth and reproduction: Cells grow and divide to create new cells.

* Response to stimuli: Cells respond to changes in their environment.

* Genetic material: Cells contain DNA or RNA, which carries their genetic information.