One thing all cells in the human body have in common is: 1. They are all designed to protect the body against disease.

2. They all expand and contract as needed.

3. They specialize in storing fat for energy for the body.

4. They have the same basic structure and components.

All of them are mostly true but I would say option 2 :)

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.