You are presented with the question "what do arthropods feed on?" and the following answer choices: 
- spiders
 - rocks
 - seeds
 - water
 - pollen
 - plankton
 - barnacles
 - food

Now knowing that bivalves feed on plankton and nonliving organic matter and bivalved arthropods are especially common, choose the best answer.


 

      plankton   