This GMAT sample question is a sentence correction practice question that tests your understanding of noun-verb agreement (number agreement) and pronouns.
Question 12: With the private space industry at the early stages of a launch revolution – it is expected that the number of launches is going to increase dramatically – it has become imperative to study the effects of the plume of exhaust that a rocket leaves in its wake on the stratosphere and the ozone layer.
Look for differences across the answer options to identify what is being tested in the sentence.
The options are differing in the construction used to suggest that a study is needed. Some options are saying “it has become imperative to study”, others are saying “studying has become imperative” and (C) removes the word “imperative” and simply says “has to be studied”
What has to be studied is also different in the sentences. Should we study the effects, the plumes or how plumes affect the ozone?
Finally, the options are different in how the underlined portion begins.
Because many more rocket launches are likely in the future, the effects of the exhaust on the stratosphere have to be studied.
The effects of the plume on the stratosphere have to be studied. An option that suggests that the plume has to be studied would be incorrect. It might well be impossible to study the actual plume because to do so will require that it be contained and not dispersed in the atmosphere.
Option (C) suggests that the plume has to be studied, when in fact, the effects on the stratosphere have to be studied.
Option (D) also suggests that the plume has to be studied – again, impossible. Option (D) also uses the singular verb “has” to refer to the two studies – of the plume and of the effect.
Option (E) does not have subject-verb agreement either. The option uses the singular verb “affects” to refer to the plural “plumes”. Moreover, both options (E) and (A) use the construction “it has become imperative”. In this construction, the pronoun “it” does not have a noun to reference and such a generic usage of the same is considered ambiguous.
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