They take in water and break it down into hydrogen and oxygen. Using their gills, they take in oxygen that is dissolved in water. They get their oxygen from the food they eat. They come to the surface every few minutes to breathe air into their lungs.
I gave my students this multiple choice question: How do most fish get the oxygen they need to survive?

Only one answer is correct among these 4 choices:
- They take in water and break it down into hydrogen and oxygen.
- Using their gills, they take in oxygen that is dissolved in water.
- They get their oxygen from the food they eat.
- They come to the surface every few minutes to breathe air into their lungs.

Could you tell me which one is correct?

Using their gills, they take in oxygen that is dissolved in water.