+ 1 for E, for using active construction and present tense 'Contribute'.

But no way under 1 min, took more than a min to get some sense from the question.

Citing, increasing, and planning happen to look parallel, but they do not have to be. Citing is a verb, increasing is an adjective (describing the mobility) and planning is a noun. If all three were being used as verbs, they would have to be parallel. However, "Citing overcomplexity, increased mobility of workers between companies, and poor financial plans" would work as well.

The parallelism here is the nouns being listed: overcomplexity, mobility, financial planning.

Whether following versions would be correct:
had contributed replaced with contributed in option A & D
estimated replaced with has estimated in option B

In option E, both contribute and contributed would be correct grammatically

The original sentence incorrectly utilizes the past perfect tense in its use of “had contributed.” The past perfect tense demands that the simple past tense also be used in the sentence to refer to another action that occurred in the past but after the action referred to by the past perfect tense. Here, the sentence uses the present perfect tense “has cited” and the present participle “estimating,” but does not use the simple past tense to refer to another action in the later past.

(A) This choice is incorrect as it repeats the original sentence.

(B) This choice is awkward in its use of the structure “Overcomplexity, increasing mobility . . . , and poor financial planning . . .have been cited” as this structure leads to the use of the passive voice, which is less preferable than the active voice. It is also problematic in its use of both the past tense “estimated” and the present perfect tense “have been cited” to refer to the recent study; the verb tenses should be consistent in their treatment of the study.

(C) This choice incorrectly places the modifying phrase “Citing overcomplexity, increasing mobility . . . and poor financial planning” adjacent to “less than half of American workers,” incorrectly suggesting that it is less than half of American workers, and not a recent study, that cites these factors as causes for a lack of contribution to retirement plans. This choice also repeats the original verb tense error with "had contributed."

(D) This choice repeats the original verb tense error with "had contributed."

(E) CORRECT. This choice correctly uses both the present participle (“Citing . . .”) and the present perfect (“has estimated”) to refer to the recent study, as well as the present tense “contribute” in reference to the study findings. The phrase “Citing overcomplexity, increasing mobility . . . , and poor financial planning,” is correctly used here as a modifier for “a recent study.”

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