According to scientists who monitored its path, an expanding cloud of energized particles ejected from the Sun recently triggered a large storm in the magnetic field that surrounds Earth. which brightened the Northern Lights and also possibly knocking out a communications satellite.

Option A
Option B
Option C
Option D
Option E

(This question is from Official Guide. Therefore, because of copyrights, the complete question cannot be copied here. The question can be accessed at GMAT Club)


Sentence Analysis

Let’s look at the sentence structure:

  • According to scientists (modifies the main clause)
    • who monitored its path, (relative clause modifying scientists)
  • an expanding cloud of energized particles (Main subject: “cloud”)
    • ejected from the Sun (verb-ed modifier modifying “particles”)
  • recently triggered a large storm (Main verb: “triggered”)
    • in the magnetic field (Modifies the main verb. Answers “Where triggered?”)
      • that surrounds Earth. (relative clause modifying “field”)
        • which brightened the Northern Lights (relative clause. Seems to modify “Earth”. Should logically modify “storm”)
        • and also possibly knocking out a communications satellite. (Logically seems to provide parallel action to “brightened”. “Knocking” is incorrect.)

The sentence presents information according to the scientists who monitored the path of a cloud of energized particles. This cloud was ejected from the sun and recently triggered a large storm. This storm happened in the magnetic field that surrounds Earth. The storm brightened the Norther Lights and possibly knocked out a communications satellite.

The sentence has the following errors:

  1. In “which brightened”, ‘which’ seems to modify the closest noun “Earth”, producing an illogical meaning that Earth brightened the Northern Lights.
  2. “knocking” is incorrect since it is not parallel to anything before “and”. In the current structure, it should be replaced by “knocked” to make it parallel to “brightened”.

Option Analysis

(A) Incorrect. For the reasons mentioned above.

(B) Incorrect. For the following problems:

  1. The use of “was what” unnecessarily twists the sentence structure. The same idea can be communicated by eliminating these words.
  2. The reference of “it” is not clear. “it” can refer to either “expanding cloud” or “large storm”. Structurally, since “it” is the subject of the independent clause, it refers to the subject of the previous independent clause i.e. “expanding cloud”. However, in such case, this option means that the cloud brightened the Northern lights. Logically, “storm” seems to be a better contended for the same.
  3. Since “it brightened…” is a separate independent clause in this option, it is not clear whether this clause is also “according to the scientists” or is something separate.

(C) Correct. This option presents “brightening” and “knocking” as verb-ing modifiers modifying the preceding clause. Both of these actions present the result of the preceding the clause. The could triggered a large storm, and as a result, these two events happened.

(D) Incorrect. For the following reasons:

  1. Since “a large storm” is the subject here, it seems now (from the non-underlined part) that the scientists monitored the path of the storm. Clearly, illogical.
  2. “it possibly knocked” is a separate independent clause. It is not joined properly with the previous independent clause. Two independent clauses cannot be joined by just “and”.
  3. This option doesn’t mention that the particles were ejected from the Sun.

(E) Incorrect. Repeats all the errors of option D.

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