GMAT Sentence Correction (SC) | Re: Women working outside the home continue to earn only about

Women working outside the home continue to earn only about tow-thirds of working men.

(A) of working men
(B) of the amount of working men
(C) of the amount working men have
(D) of the amount earned by working men
(E) what has been earned by working men

may be D nut why not B ?

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