When an enzyme reacts with only limited, selected substrates, this characteristic is referred to as the enzyme's

When an enzyme reacts with only selected and limited number of substrates, then this characteristic of the enzyme is referred to as its specificity. The enzymes which are specific, catalyzes only selected few reactions. These enzymes are specific to certain bonds or functional groups. Some enzymes have absolute specificity, which means that they catalyze only one reaction.

Hence, the blank can be filled with 'specificity'.

answer; hypnagogic sensations)

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.