If some animals have excretory structures that conserve water and elminate waste, then what is the name of something some animals use to conserve water and elminate waste?

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

 

      excretory structures    