gmat_perfect wrote:A recently published report indicates that the salaries of teachers continue to lag far behind other college-educated professionals, because they make an average of nearly $8,000 a year less at the start of their careers and almost $24,000 less a year by the time they reach the age of 50.

(A) other college-educated professionals, because they make an average of nearly $8,000 a year less at the start of their careers and almost $24,000 less
(B) other college-educated professionals, by an average of nearly $8,000 a year at the start of their careers, to almost $24,000
(C) what other college-educated professionals are paid--making an average of nearly $8,000 a year less at the start of their careers and almost $24,000 less
(D) those of other college-educated professionals--by an average of nearly $8,000 a year at the start of their careers to almost $24,000 less
(E) those of other college-educated professionals--by an average of nearly $8,000 a year at the start of their careers, and by almost $24,000

[spoiler]OA: E[/spoiler]

Why are the wrong options wrong?

Specific question:

by X and by Y should be correct, but in the option E, "By X, and by Y" has been used. Is it correct to use in this way?

Thanks.