Sentence Correction

Although blue herons can still be found along the Maine coast, their population has declined dramatically when compared to the 1970's, a period in which there were fewer bald eagles competing with them for food and nesting sites.

A their population has declined dramatically when compared to the 1970s
B their population has declined dramatically compared with the 1970s
C their populations have declined dramatically since the 1970s
D their populations have declined in comparison to those of the 1970s
E their population has declined in comparison with that of the 1970s


Pls provide your answer with explanation

Answers A and B are incorrect. They compare "their population" with the 1970s. Answer C is the correct choice. It is grammatically correct and the most concise, although it includes a slight change in meaning (change from "population" to "populations"). Answers D and E are correct grammatically but they are redundant in comparison to answer C. Moreover, they don't include the adverb "dramatically" so the meaning is changed more significantly than in the correct answer.

Thanks Kasia for the below explanation but I have some concerns :-

Is "Populations" the correct usage ? the word "population" is itself plural. Pls. clarify !!

The use of the plural form "populations" does slightly change the meaning but this change is just a minor flaw and not a serious mistake. The plural form "populations" may be referring to a few populations of herons living along the Maine coast.

To kasia
good day
u said that D and E are gramitically correct but redundant .plz tell me how is it that when i read them literally i get a very awkward meaning
for example in E : their population has declined in comparison with that of the 1970s

"that" can refer to only to "population" and not "their population"
so the the option E becomes : their population has declined in comparison with population of the 1970s
now i feel that E as written above gives a very strange meaning

i can corroborate my reasoning with the following example : japan's population is shrinking faster than that of any other nation

in this sentence "that" refer to population and not to "japan's population"

kindly guide me
thanks and regards

Tell me the source of the question beacsue each statement has minor flaws and its hard to choose the right one. D and E is wrong because the two sentences omitted "dramatically. however, these two are grammaticaly right. i will be surprised if this question is from OG. Gmat hardly use "populations" because population itself is plural. it wasnt a hard question but to get to the right choice is hard.

"population" is a collective noun and can be singular
population of united states has increased

sana.noor wrote:Tell me the source of the question beacsue each statement has minor flaws and its hard to choose the right one. D and E is wrong because the two sentences omitted "dramatically. however, these two are grammaticaly right. i will be surprised if this question is from OG. Gmat hardly use "populations" because population itself is plural. it wasnt a hard question but to get to the right choice is hard.

This question comes from Vertias Prep Question Bank !!