Once considered the ninth planet in the solar system, Pluto was discov

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Here is a detailed explanation to this question-

Meaning is crucial to solving this problem:
Understanding the intended meaning is key to solving this question; the intended meaning of this sentence is that Pluto was discovered in 1930, once considered the ninth planet in the solar system, and lost its planetary status in 2006, a development that prompted the International Astronomical Union (IAU) to create a new definition for the term "planet", and Pluto is now categorized as just one out of 70,000 icy objects in the Kuiper Belt that measure 100 kilometers across or more.

Concepts tested here: Meaning + Modifiers + Tenses

• "who/whose/whom/which/where", when preceded by a comma, refer to the noun just before the comma.
• In a “noun + comma + phrase” construction, the phrase must correctly modify the noun; this is one of the most frequently tested concepts on GMAT sentence correction.
• If a list contains only two elements, they must be joined by a conjunction.
• Information that is permanent in nature is best conveyed through the simple present tense.
• The simple past tense is used to refer to events that concluded in the past.

A: This answer choice incorrectly modifies "2006" with "which prompted the International Astronomical Union..." planet", illogically implying that the year 2006 prompted the International Astronomical Union (IAU) to create a new definition for the term "planet"; the intended meaning is that Pluto losing its planetary status prompted the International Astronomical Union (IAU) to create a new definition for the term "planet"; please remember, "who/whose/whom/which/where", when preceded by a comma, refer to the noun just before the comma. Further, Option A incorrectly uses the present participle ("verb+ing" - "measuring" in this sentence) to refer to information that is permanent in nature; please remember, information that is permanent in nature is best conveyed through the simple present tense.

B: Correct. This answer choice modifies the verb phrase "lost its planetary status in 2006" with "a development that prompted..."planet", conveying the intended meaning - that Pluto losing its planetary status prompted the International Astronomical Union (IAU) to create a new definition for the term "planet". Moreover, Option B uses the clause "Pluto...is now categorized as...100 kilometers across or more", conveying the intended meaning - that Pluto is now categorized as just one out of 70,000 icy objects in the Kuiper Belt that measure 100 kilometers across or more. Further, Option B correctly uses the simple past tense verb "prompted" to refer to an event that concluded in the past. Additionally, Option B correctly uses the simple present tense verb "measure" to refer to information that is permanent in nature. Besides, Option B correctly uses a conjunction ("and" in this sentence) to join two elements in a list -- the verb phrases "lost its planetary status in 2006" and "is now categorized...100 kilometers across or more".

C: This answer choice incorrectly modifies "the term "planet"" with "now categorized as...100 kilometers across or more", illogically implying that the term "planet" is now categorized as just one out of 70,000 icy objects in the Kuiper Belt that measure 100 kilometers across or more; the intended meaning is that Pluto is now categorized as just one out of 70,000 icy objects in the Kuiper Belt that measure 100 kilometers across or more; please remember, in a “noun + comma + phrase” construction, the phrase must correctly modify the noun. Further, Option C incorrectly uses the present participle ("verb + ing" - "prompting" in this sentence" to refer to an action that concluded in the past; please remember, the simple past tense is used to refer to events that concluded in the past. Additionally, Option C incorrectly uses the infinitive verb form ("to + base form of verb" - "to + measure" in this sentence) to refer to information that is permanent in nature; please remember, information that is permanent in nature is best conveyed through the simple present tense.

D: This answer choice fails to use a conjunction to join two elements in a list -- the verb phrases "lost its planetary status in 2006" and "is now categorized...100 kilometers across or more". Further, Option D incorrectly uses the infinitive verb form ("to + base form of verb" - "to + measure" in this sentence) to refer to information that is permanent in nature; please remember, information that is permanent in nature is best conveyed through the simple present tense.

E: This answer choice alters the meaning of the sentence through the clause "Pluto...prompted...a new definition for the term "planet"; the construction of this clause illogically implies that Pluto prompted the International Astronomical Union (IAU) to create a new definition for the term "planet"; the intended meaning is that Pluto losing its planetary status prompted the International Astronomical Union (IAU) to create a new definition for the term "planet".

Hence, B is the best answer choice.

To understand the concept of "Simple Tenses" on GMAT, you may want to watch the following video (~1 minute):



All the best!
Experts' Global Team