Snails, when repeatedly touched with no harm intended, stop pulling their heads back into their shells. what type of behavior does this example represent?

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.

just finished the test, the answer is d, greg is the least cost-effective because he charges the most for the project