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

Fact 2: Crustaceans are predominantly aquatic, breathing by means of gills.

Given the two facts above, answer the question "Crustaceans breathe what through their gills?" with the following options: 
- matter
 - water
 - saliva
 - gametes
 - semen
 - liquid
 - oxygen
 - air


 

  water       