You are presented with the question "What are gills used for breathing by sharks?" and the following answer choices: 
- air
 - mussels
 - carbon monoxide
 - lava
 - fish
 - open
 - water
 - squids

Now knowing that gills are used for breathing water by aquatic animals and shark exhibit Come face to face with the ultimate aquatic predator, choose the best answer.


 

       water  