Q: 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, crustaceans breathe what through their gills?

Choose your answer from:
1). matter
2). water
3). saliva
4). gametes
5). semen
6). liquid
7). oxygen
8). air
A:
2).