- A fish is a kind of aquatic animal
- Gills are used for breathing water by aquatic animals
- Therefore, gills are a part of a fish used for breathing water

- Gills are a part of a fish used for breathing water
- Breathing is when a gill converts from oxygen in water into oxygen in blood
- Therefore, gills are a part of a fish used for breathing oxygen in water

- Gills are a part of a fish used for breathing oxygen in water
- In water means underwater
- Therefore, gills are a part of a fish used for breathing oxygen underwater

- An animal requires oxygen for survival
- Adaptations are used for survival
- Hence, an example of an adaptation is something that is used for getting oxygen

- Gills are a part of a fish used for breathing oxygen underwater
- An example of an adaptation is something that is used for getting oxygen
- Hence, gills are a kind of adaptation for getting oxygen underwater

So, gills are a kind of adaptation for getting oxygen underwater
Which adaptation allows a fish to get oxygen underwater?
- An animal requires oxygen for survival 
- Breathing is when a gill converts from oxygen in water into oxygen in blood 
- A fish is a kind of aquatic animal 
- In water means underwater 
- Gills are used for breathing water by aquatic animals 
- Adaptations are used for survival