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

Guys ,

Can you pls explain me more why right and why wrong . In this ques i am not able to eliminate the options and not able any rule and logic , don't know why?

OAE