Are made up of a gel-and water-filled nucleus surrounded by a series of fibrous rings. nerve roots core muscles intervertebral disks spinal curves

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.

equal distribution i think.