Cara and Chuck were looking at pond water through a microscope. They saw small square crystals in their slide. Cara wondered what it was. Chuck said it could not be any living thing because it was not

Chuck said it could not be any living thing because it was not made of cells.

Explanation:

The main characteristic on the basis of which living things are separated from non - living things is the presence of cells in living things. A living thing might be made up of only one cell like prokaryotes or it might be made of multiple cells like eukaryotes. Most likely, a crystal structure won't have any cells or organelles in it. Hence, Chuck can tell that the small square crystal is not a living thing.