Given a scientific question, generate a correct answer to it.

Example Input: Oxygenated air, taken in during inhalation, diffuses across the surface of the lungs into the what?
Example Output: bloodstream

Example Input: The nitrogen that enters living systems by nitrogen fixation is successively converted from organic nitrogen back into nitrogen gas by what?
Example Output: bacteria

Example Input: Fibrous root systems have many small branching roots called what?
Example Output:
fibrous roots