Here's the
official explanation provided by the GMAC for this question:
The given sentence reports that the editor of
Science and Children projects a drop of 35 percent in the number of science and mathematics teachers within five years, a projection based on a 4 percent reduction seen last year. Points to consider include the following: Is the modifying phrase
based on … year grammatically correct in this context? Is the preposition
of with the noun
reduction a correct usage? Is
reduction … of teachers correct diction?
Option A: Some would argue that
based on … year is an adjectival phrase modifying the noun
Phyllis Marcuccio and is therefore incorrect in this context. But current well-established usage allows this phrase to be treated as adverbial, modifying the verb
projects. More significant issues arise in the phrase
reduction of … teachers. The compressed phrasing permits absurd but unintended readings, whereas the intended reading is surely
a reduction in the number of … teachers.Option B: Does
teachers were reduced by 4 percent mean that the teachers diminished in stature or status? What is surely be intended is that the number of such teachers decreased, not that the teachers themselves were somehow reduced.
Option C: The phrasing
science and mathematics teachers being reduced … year is unnecessarily awkward, wordy, and confusing, failing to convey clearly that the reduction applies to the
number of teachers.
Option D: Correct. The phrasing
reduction in the number of … teachers is correct. The phrase
on the basis of …
year is a grammatically and rhetorically appropriate adverbial modifier of the verb
projects.Option E: The preposition
of is incorrect with
reduction; the correct preposition is
in. Some would argue that
based on … year is an adjectival phrase modifying the noun
Phyllis Marcuccio and is therefore incorrect in this context. But current well-established usage allows this phrase to be treated as adverbial, modifying the verb
projects. The correct answer is D.
Please note that I'm not the author of this explanation. I'm just posting it here since I believe it can help the community.