Plz answer I need help​

1.Fish gills are organs that allow fish to breathe underwater. Most fish exchange gases like oxygen and carbon dioxide using gills either on side of the pharynx.

2.Gills are branching organs located on the side of fish heads that have many, many small blood vessels called capillaries.

3.The colour is red

4. A Gill filaments project from each arc between the dorsal upper and ventral lower surfaces of the filaments.

It's cell theory. easy name i would think.

They must use the scientific method