Good question - and I should point out that this question is from a healthy 10+ years ago so it may not be fully reflective of today's GMAT.

The problems with E are a little more stylistic than binary. It:

-Uses the passive voice
-Ends the object with a preposition (which isn't technically *wrong* but it's awkward)
-Inserts the modifier "by consumers" in a pretty clumsy fashion

D, by contrast, is direct. The active subject "a consumer" leads and fixes the glaring pronoun reference error from the original sentence.

As far as the pronoun structure in D...it's definitely not wrong. You'd definitely be able to say things like "I thought I'd struggle on the verbal section, but it was actually easier than I expected." - where "it", the subject of the second clause, refers to the object of the first. So that's not at all grounds for dismissal of choice D. And if you're comparing D and E directly, D is cleaner and more direct...I wouldn't make "passive voice" or "clumsy construction" your primary decision points, but if you're between D and E, E has a lot more to be skeptical about.

Here's a previous discussion on this same question that may help, too: https://www.beatthegmat.com/verbal-revie ... 86160.html