PREP2 133 的逗号问题！

gcen

133.      (31827-!-item-!-188;#058&006534)







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

版主您好我想请教一下PREP2 133,这里为什么是BY...,AND BY...结构， 其中，的作用的什么，虽然也见过PERP中有类似的结构比如even with A, and with B 结构  但是为什么要用都好隔开呢？直接并列不是更好没有歧义吗？
谢谢！

lcy19812000

I think "to almost $24,000 less"  in D has two different meanings in the sentence.

1. It says the gap is $24,000 when they are 50 years old .

2. It says the gap has increased by $24,000 from $8,000. In another word, the gap of payment when they are 50 years old is $32,000.