Numerous studies have shown that the income levels of working adults who were students of average academic ability often surpass the income levels of those adults who were once students of exceptional academic abilities.
(A) the income levels of those adults who were once students of exceptional academic abilities
(B) those of adults who had been exceptionally able students academically
(C) those of adults who were students of exceptional academic ability
(D) adults who were students of exceptional academic ability
(E) the incomes of adults who had been students of exceptional academic ability
This following is the explanation for (E)
(E) This choice incorrectly uses the past perfect tense “had been," which is unjustified and also not parallel to the non-underlined simple past tense verb "were."
My Question:
I got this answer correct by using parallelism/comparison rules but one thing that I can't wrap my head around is in the explanation for (E) (and B for that matter) it says "this choice incorrectly uses the past perfect tense "had been".
I don't quite understand why "had been" is wrong... it sounds worse than using "were" but I don't quite understand the technicality behind it.
Can someone please explain? Maybe by including examples of other sentences where "had been" can and cannot be used.
Thank you in advance!