Why I can't go with option (d). Without 'by you' in the passive voice of the sentence , it is still having the same meaning without any ambiguity.Please explain.
Option D contains less information than the original sentence. The original sentence implies that "you" should have brought it to my attention. However, option D simply asks why "someone" didn't bring it to my attention.
There's nothing grammatically wrong with D. It just isn't the most exact restatement of the original sentence.