Fact 1: Mollusks are a major food source for other organisms, including humans.

Fact 2: Mollusks filter the water as they look for food.

Given the two facts above, answer the question "Members of a major food source for humans filter what?" with the following options: 
- gills
 - salmon
 - matter
 - water
 - Air
 - energy
 - sodium
 - Energy.


 

    water     