Respuesta :

Answer: B- nitrogen 

Answer choices are:

A- water 
B- nitrogen 
C- carbon 
D- phosphorus

The idea of helping someone to get some help in return resulting to close interactions is a symbiotic relationship. In a symbiotic relationship, the two species in the relationship like bacteria and legumes live together.

Legumes have root nodules that provide a home for bacteria (rhizobia).   Rhizobia that fixes nitrogen. They convert nitrogen gas from the atmosphere into ammonia. This ammonia is in turn used in the formation of amino acids and nucleotides in legumes. This is the nitrogen  cycle which involves a symbiotic relationship between bacteria and