Here at the GMAT Project, we know a thorough knowledge of English grammar is essential to excelling on the GMAT, especially when it comes to Sentence Correction questions. These questions present you with a sentence in which a portion of the sentence is underlined. The underlined portion may or may not contain an error; if it does, you must pick the best revised version of that portion of the sentence from among the answer choices. If the original sentence is correct, you should choose answer choice (A), which always simply restates the original version of the underlined portion of the sentence. Consider, for instance, the following example:
“Pulsars are generally believed to be fast-spinning neutron stars to be located by the pulsating radio waves it emits.”
(A) to be located by the pulsating radio waves it emits
(B) to be located by the pulsating radio waves they emit
(C) locatable by the pulsating radio waves it emits
(D) emitting pulsating radio waves by which it can be located
(E) that can be located by the pulsating radio waves they emit
The original version of the underlined portion of the sentence contains two main errors. First, it incorrectly begins with the infinitive form of the verb “to be.” An infinitive usually comprises part of a verb phrase that includes a conjugated verb with which it belongs. For instance, consider the correctly used infinitive that appears earlier in the sentence: “Pulsars are generally believed to be fast-spinning neutron stars…” In this case, the conjugated verb is “believed,” which is paired with the infinitive “to be” in order to express that scientists generally think pulsars belong to a certain class of astronomical phenomena. While it is true that a single conjugated verb may take multiple infinitives, these infinitives must be joined with an appropriate conjunction. For instance, one could say that “Pulsars are generally believed both to be fast-spinning neutron stars and to appear very luminous in the night sky.” There is no conjunction joining them in the original sentence, and even if the first infinitive were removed, the resulting sentence would be nonsense: “Pulsars are generally believed to be located by the pulsating radio waves it emits.” The intended meaning of the sentence is unclear, which always indicates an error. From this, we can eliminate choices (A) and (B).
The second error has to do with the pronoun “it” in the underlined portion of the sentence: “to be located by the pulsating radio waves it emits.” All pronouns refer back to an actual noun: one of their main purposes in English is to allow us to avoid repeating nouns over and over again. The noun to which a pronoun refers is called its antecedent. In this sentence, what is the intended antecedent of the pronoun “it” in question? In other words, what is emitting pulsating radio waves? The pulsars are, of course. However, “pulsars” is a plural noun, and “it” is a singular pronoun. Thus, we have a pronoun that disagrees with its antecedent in number. This is not allowed. “It” should be replaced with the appropriate plural third person nominative case pronoun, “they.” From this, we can eliminate choices (C) and (D), which both persist in erroneously using the singular pronoun, “it.”
Choice (E), by process of elimination, must be correct, and indeed it is. It correctly uses “they” to refer to the pulsars, and it replaces the nonsensical infinitive “to be” with “that can be.” The relative pronoun “that” correctly begins a relative clause (What can be located by the pulsating radio waves they emit? The stars can be located by the pulsating radio waves they emit!). Thus, choice (E) is best.
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