Correct Option DSince 1992,
in an attempt
to build up
the Atlantic salmon population in
-
each of the seven rivers in which salmon still spawn,
state officials in Maine have stocked
-
each river with fry raised in hatcheries from eggs produced by wild fish found in that
particular riverOption A:
Them - Wrong
Pronoun Them is ambiguous, to what it is refer to, either it is the State officials who has stocked, or salmon which is stocked or the eggs of wild fish.
Option B:
the river - Wrong
Sentence demands singular Subject "river" but the intended meaning of sentence is to each of seven rivers where salmon still spawn, the official have taken stock at each seven rivers, not only just the one river.
Option C :
the rivers - Wrong
rivers is plural, which logically refer to group of 7 river mentioned, but again the meaning error occurs, which logically need to correct by placing singular river, as the official have stocked at each individual river, not the rivers
Option D:
each river -
CorrectClear information, parallelism with each of the rivers, describes as singular, and makes intended meaning clear.
Option E:
that river - Wrong
Utilisation of
that to introduce river can be avoided, as that is used to provide essential information of the sentence.