On GMAT Sentence Correction section, watch out for prepositional phrases in the middle of sentences, especially those bracketed by commas. They often can refer to either the first or second half of the sentence, creating ambiguity.
Take a look at this GMATPrep® question:
Although various eighteenth- and nineteenth-century American poets had professed an interest in Native American poetry and had pretended to imitate Native American forms in their own works, until almost 1900, scholars and critics did not begin seriously to study traditional Native American poetry in native languages.
(A) until almost 1900, scholars and critics did not begin seriously to study
(B) until almost 1900 scholars and critics had not begun seriously studying
(C) not until almost 1900 were scholars and critics to begin seriously to study
(D) it was not almost until 1900 when scholars and critics began to seriously study
(E) it was not until almost 1900 that scholars and critics seriously began studying
Let’s take a look at our answer choices.
Until almost 1900 is really just the preposition until plus the object of the preposition, 1900, with the adjective almost modifying 1900 in between. Therefore, we can treat the phrase like any other preposition. The problem with choice A is that it is not clear what until almost 1900 is modifying. Is it modifying the clause before it (had pretended to imitate Native American forms in their own works) or the clause after it (scholars and critics did not begin seriously to study traditional Native American poetry in native languages)? There’s no way to know, so the placement of the prepositional phrase is ambiguous.
We can eliminate B because until almost 1900 is a prepositional phrase that comes before the independent clause it modifies. When a modifier or dependent clause comes before the independent clause, it needs to be set off by a comma. For example, “Until midnight, I read my book.” However, in this case, the comma would create the same modification error in B that choice A contains, so either way B would be incorrect. Choice C contains the awkward construction to begin seriously to study.
The first problem with choice D is that not almost until 1900 is an awkward construction because not seems to negate almost instead of until in this construction, and almost seems to refer to the entire prepositional phrase instead of just the object of the preposition, 1900. Not until almost 1900 in E is preferable. The second problem with D is the word “when.” The relative clause when scholars and critics began to seriously study does not describe 1900 as a period of time. Instead, the clause describes an event that began around that time.
On the GMAT, “when” is usually used to describe one situation that happens at the same time as another; the word is only rarely used as a relative pronoun. “When” should only be used as a relative pronoun when it introduces a relative clause that actually describes the time in question. For example:
The weeks when I was happy to watch TV all day are long gone.
An easy way to test whether “when” has correctly been used as a relative pronoun is to replace it with “in which.” The above sentence would read:
The weeks in which I was happy to watch TV all day are long gone.
This construction makes sense. In the case of our GMAT question, however, replacing “when” with “in which” creates an illogical clause:
It was not until almost 1900 in which scholars and critics seriously began studying…
Choice E is correct. The prepositional phrase not until almost 1900 is correctly worded and properly placed, and the verb began is in the simple past tense to contrast the past perfect tense (had professed and had pretended) used to describe the preceding period. Though at first glance the pronoun it may appear ambiguous, in fact the pronoun logically refers to the upcoming noun clause that scholars and critics seriously began studying traditional Native American poetry in native languages.