Dna is characterized by a single helix and ribose sugars

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.

yes it is   dangerous

explanation:

because that foot is discusting and could get you sick

1. efficient use of space

2. elimination of groundwater contamination

3. energy generation

4. lower carbon footprint