Quote:
In the mid-1980’s, since bats were overwhelmed by noxious gases, and routinely falling from the sky above Vegas freeways, this prompted police officials to devise a plan that reduced emissions.
Quote:
A. since bats were overwhelmed by noxious gases, and routinely falling from the sky above Vegas freeways, this prompted police officials to devise a plan that reduced
and routinely falling from the sky : is not a clause. it's not parallel to "since bats were overwhelmed by noxious gases". Also, it leaves the meaning incomplete.
Quote:
B. since bats that had been overwhelmed by noxious gases were routinely falling from the sky above Vegas freeways, it prompted police officials to devise a plan that would reduce
What is "it" ? No logical noun antecedent.
Quote:
C. bats had been overwhelmed by noxious gases and routinely fell from the sky above Vegas freeways, prompting police officials to devise a plan that reduced
I find the use of "had been" questionable. It implies that the action over overwhelming was done to the bats (by another agent, probably intentionally) prior to something else that happened in the past. While, that something else can be "fell", the other aspect of the meaning (the agent carrying out the action of overwhelming the bats) is not clear. We can hold on to it for now, but we will see in a minute why E is better.
Quote:
D. bats overwhelmed by noxious gases and routinely falling from the sky above Vegas freeways were prompting police officials to devise a plan to reduce
Here, overwhelmed by and routinely falling are used as modifiers, and grammatically correct. But "were prompting" suggests that the bats themselves were prompting, where the intended meaning is the prompt was actually the result of the bats falling. In other words, bats did not intentionally prompt the officers, but the wording of this option suggests they did. So, D is out
Quote:
E. bats overwhelmed by pollution routinely fell from the sky above Vegas freeways, prompting officials to devise a plan to reduce
This is the correct answer. "overwhelmed by pollution" is used as modifier, without requiring an agent to intentionally carry out the action. This corrects the issue in C. Moreover, prompting officials is used as a , ing modifier to show the result of the bats falling (thereby correcting the issue with D).