OFFICIAL EXPLANATION
Reading not only improves language skills but also develops the imagination by requiring the visualization of a reality previously unknown by the reader.A. not only improves language skills but also develops the imagination by requiring the visualization of a reality previously unknown by
This answer choice is grammatically incorrect. The correct preposition to use after the adjective unknown is to.B. improves language skills but also develops the imagination by requiring the visualization of a reality previously unknown to
Although this answer choice corrects the original Preposition error by replacing the preposition by with to, it is still grammatically incorrect. But also must be preceded by not only.
What helps us identify this question as a Parallelism question as well as identify the mistake is the following Stop Sign: not only... but also...C. not only improves language skills but also development of the imagination by requiring the visualization of a reality previously unknown to
Although this answer choice corrects the original Preposition error by replacing the preposition by with to, it is still grammatically incorrect. The same part of speech that follows not only must also follow but also. In this answer choice, not only is followed by the verb improves. But also, however, is followed by the noun development.
What helps us identify this question as a Parallelism question as well as identify the mistake is the following Stop Sign: not only... but also...D. not only improves language skills but develops the imagination by requiring the visualization of a reality previously unknown to
Although this answer choice corrects the original Preposition error by replacing the preposition by with to, it is still grammatically incorrect. Not only must be followed by but also, not just but.
What helps us identify this question as a Parallelism question as well as identify the mistake is the following Stop Sign: not only... but also...E. not only improves language skills but also develops the imagination by requiring the visualization of a reality previously unknown to
The original sentence contains a Preposition error. The correct idiom is X is unknown to Y.
Example: The author's identity is unknown to the public.
Apart from correcting the above error, this answer choice maintains Parallelism while using the structure not only X...but also Y.