You are presented with the quiz "What does rhizobial bacteria do for plants?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "bacteria in soil convert atmospheric nitrogen into a form usable by plants" and "rhizobial bacteria convert atmospheric nitrogen into nitrate fertilizers in a form usable by plants". 

So, what's the best answer to the question?


 

    Converts nitrogen       