Fact 1: Gills are used for breathing water by aquatic animals.

Fact 2: Shark exhibit Come face to face with the ultimate aquatic predator.

Given the two facts above, answer the question "What are gills used for breathing by sharks?" with the following options: 
- air
 - mussels
 - carbon monoxide
 - lava
 - fish
 - open
 - water
 - squids


 

       water  