Emigration has occurred in an ecosystem when individual
a. move into the ecosystem
b. are born healthy
c. die of disease
d. leave the ecosystem

The answer is D, leave the ecosystem.

I hope this helps. :)

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.