You are presented with the question "bacteria in soil converts atmospheric nitrogen into a form usable by what?" and the following answer choices: 
- bacteria
 - humans
 - density
 - Conifers
 - Roundworms
 - gravity
 - h2o
 - orchids

Now knowing that bacteria in soil convert atmospheric nitrogen into a form usable by plants and many orchids are rewarding indoor plants, choose the best answer.


 

        orchids 