Respuesta :
Selection A is the most accurate. Nitrogen in the atmosphere cannot be used by most living things. For example, plants require nitrogen ions to function, and can only receive it through their roots. Atmospheric nitrogen does not provide an avenue for this uptake. Bacteria provide the nitrogen fixating needed for plants to be able to receive the proper form of nitrogen.
Bacteria are needed in the nitrogen cycle because other living things cannot use atmospheric nitrogen.
Nitrogen fixation
As far as nitrogen fixation is concerned, only bacteria are able to fix atmospheric nitrogen into forms usable by other living organisms.
They convert atmospheric nitrogen into chemical forms usable by plants.
Some bacteria fix nitrogen through symbiotic association with the root nodules of leguminous plants while others fix it by non-symbiotic association.
More on nitrogen fixation can be found here: https://brainly.com/question/4191267