You are presented with the question "What is the name of something some animals use to conserve water and elminate waste?" and the following answer choices: 
- it keeps an organism warm
 - food and shelter
 - Exfoliation
 - an area swollen with pus
 - swamp vegetation
 - excretory structures
 - reusing materials
 - colder and wetter

Now knowing that some arthropods have special excretory structures and terrestrial arthropods have an excretory system that conserves water and eliminates waste, choose the best answer.


 

      excretory structures   