Sentence Correction

Students in the metropolitan school district lack math skills to such a large degree as to make it difficult to absorb them into a city economy becoming ever more dependent on information-based industries.

(A) lack math skills to such a large degree as to make it difficult to absorb them into a city economy becoming
(B) lack math skills to a large enough degree that they will be difficult to absorb into a city's economy that becomes
(C) lack of math skills is so large as to be difficult to absorb them into a city's economy that becomes
(D) are lacking so much in math skills as to be difficult to absorb into a city's economy becoming
(E) are so lacking in math skills that it will be difficult to absorb them into a city economy becoming

[spoiler]i recognized the idioms and chose E but at the last moment i changed my answer to D because E uses "city economy" instead of "city's economy". Can you explain this[/spoiler]

A city economy is just fine here. It acts as an adjective to describe the economy. You can have an agricultural economy, rural economy, etc.

agricultural and rural are adjectives but city is a noun https://dictionary.reference.com/browse/city

vikram4689 wrote:Students in the metropolitan school district lack math skills to such a large degree as to make it difficult to absorb them into a city economy becoming ever more dependent on information-based industries.

(A) lack math skills to such a large degree as to make it difficult to absorb them into a city economy becoming
(B) lack math skills to a large enough degree that they will be difficult to absorb into a city's economy that becomes
(C) lack of math skills is so large as to be difficult to absorb them into a city's economy that becomes
(D) are lacking so much in math skills as to be difficult to absorb into a city's economy becoming
(E) are so lacking in math skills that it will be difficult to absorb them into a city economy becoming

[spoiler]i recognized the idioms and chose E but at the last moment i changed my answer to D because E uses "city economy" instead of "city's economy". Can you explain this[/spoiler]

A noun can serve as an adjective:
SOCCER player
HISTORY book
COMPUTER keyboard
In all of these examples, the first noun serves as an adjective modifying the second noun.

In the OA, city serves as an adjective modifying economy.
Thus, CITY economy is correct.

Thanks Mitch, are city's economy and city economy both legitimate for correct answer. Also any tips on how can i avoid falling in such a trap

vikram4689 wrote:Thanks Mitch, are city's economy and city economy both legitimate for correct answer. Also any tips on how can i avoid falling in such a trap

In the SC above, a city's economy becoming and a city's economy that becomes are INCORRECT.

Avoid the following constructions:
POSSESSIVE MODIFIER + NOUN + NO COMMA + VERBing.
POSSESSIVE MODIFIER + NOUN + NO COMMA + THAT clause.

Generally, if a POSSESSIVE MODIFIER + NOUN construction is to be modified further, the additional modifier(s) will be NON-ESSENTIAL and thus should be preceded by a COMMA:

INCORRECT: Critics have praised the author's book flying off bookshelves.
CORRECT: Critics have praised the author's book, which is flying off bookshelves.

Mitch,
Please explain why such construction is INCORRECT

INCORRECT: Critics have praised the author's book flying off bookshelves.

vikram4689 wrote:Mitch,
Please explain why such construction is INCORRECT

INCORRECT: Critics have praised the author's book flying off bookshelves.

Critics have praised the author's book.

On its own, this sentence conveys the essential meaning: it is clear that one specific book is being discussed -- the author's book -- and that critics have praised this book.

That the book is flying off bookshelves is not essential to the meaning of the sentence.
Generally, a NON-ESSENTIAL modifier should be preceded by a comma:

Critics have praised the author's book, which is flying off bookshelves.

may be i didn't express myself clearly, my questions
a) WHAT is the reason that below constructions are to be avoided and
b) WHY they are incorrect in original sentence

In the SC above, a city's economy becoming and a city's economy that becomes are INCORRECT.
Avoid the following constructions:
POSSESSIVE MODIFIER + NOUN + NO COMMA + VERBing.
POSSESSIVE MODIFIER + NOUN + NO COMMA + THAT clause.

what is the OA? A or E?

vikram4689 wrote: WHY they are incorrect in original sentence

Answer choice E:
Students in the metropolitan school district are so lacking in math skills that it will be difficult to absorb them into a CITY economy becoming ever more dependent on information-based industries.
Here, city serves as an adjective describing the TYPE OF ECONOMY found in the metropolitan school district.

Below is the OA with a city economy replaced by A CITY'S economy:
Students in THE METROPOLITAN SCHOOL DISTRICT are so lacking in math skills that it will be difficult to absorb them into A CITY'S economy.
A CITY'S economy implies not a TYPE of economy but the economy of AN ACTUAL CITY.
This creates confusion: the students here are not in A CITY but in THE METROPOLITAN SCHOOL DISTRICT.
So while the students are part of a CITY economy (the type of economy found in the school district), they are not necessarily part of a CITY'S economy (since they don't necessarily live in a city but only in the school district).
Hence, a city's economy does not convey the intended meaning.

vikram4689 wrote:may be i didn't express myself clearly, my questions
a) WHAT is the reason that below constructions are to be avoided and

Avoid the following constructions:
POSSESSIVE MODIFIER + NOUN + NO COMMA + VERBing.
POSSESSIVE MODIFIER + NOUN + NO COMMA + THAT clause.

Please see my earlier post.
Generally, POSSESSIVE MODIFIER + NOUN should not be followed by an essential modifier.
Hence, the two constructions above are unlikely to be correct.

thanks mitch, but " A CITY'S economy " uses indefinite article "A" so how " A CITY'S economy " refers to a particular city's economy and " A CITY economy " refers to general city economy

vikram4689 wrote:thanks mitch, but " A CITY'S economy " uses indefinite article "A" so how " A CITY'S economy " refers to a particular city's economy and " A CITY economy " refers to general city economy

Please revisit the post to which you're referring; I've amended it to clarify the reasoning.

Please note that the distinction between a city economy and a city's economy is NOT of the sort that I would encourage you to seek out on the GMAT.
Look for more obvious reasons to eliminate answers.