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Here is a detailed explanation to this question-
sivasanjeev
Now the fourth most important crop worldwide after wheat, rice and corn, potatoes are expected to supply even a larger share of the world's nutritional requirements in the next century if genetic engineering can increase its immunity to disease and expand its range of growing habitats.
A. potatoes are expected to supply even a
B. potatoes will, it is expected, supply an even
C. it is expected that potatoes will supply an even
D. the potato is expected to supply an even
E. expectations are for the potato to supply even a
Meaning is crucial to solving this problem:Understanding the intended meaning is key to solving this question; the intended meaning of the crucial part of this sentence is that potatoes are now the fourth most important crop worldwide after wheat, rice, and corn, and they are expected to supply a share of the world's nutritional requirements that is even larger than the share they supplied before.
Concepts tested here: Meaning + Modifiers + Grammatical Construction + Awkwardness/Redundancy• In a “phrase + comma + noun” construction, the phrase must correctly modify the noun; this is one of the most frequently tested concepts on GMAT sentence correction.
• A comma cannot join two independent clauses; such usage leads to the error of comma splice; to correct this error, the comma must be replaced with a semicolon or comma followed by a conjunction such as "and", "but" etc.
• Presenting a modifying phrase between two commas is a correct way to insert extra information into an independent clause.
A: The sentence formed by this answer choice alters the meaning of the sentence through the phrase "even a larger share"; the construction of this phrase incorrectly implies that potatoes are expected to supply a larger share of the world's nutritional requirements,
in addition to something else; the intended meaning is that potatoes are expected to supply a share of the world's nutritional requirements
that is even larger than the share they supplied before.
B: This answer choice incorrectly uses a pair of commas to insert the independent clause "it is expected" into the independent clause "potatoes will supply an even larger share"; remember, a comma cannot join two independent clauses; such usage leads to the error of comma splice; to correct this error, the comma must be replaced with semicolon or comma followed by a conjunction such as "and", "but" etc, and presenting a modifying phrase between two commas is a correct way to insert extra information into an independent clause.
C: This answer choice incorrectly uses "Now the fourth most important crop worldwide after wheat, rice and corn" to modify the placeholder pronoun "it", producing an incoherent meaning; the intended meaning is that potatoes are now the fourth most important crop worldwide after wheat, rice, and corn; remember, in a “phrase + comma + noun” construction, the phrase must correctly modify the noun.
D: Correct. This answer choice correctly uses "Now the fourth most important crop worldwide after wheat, rice and corn" to modify "potatoes", conveying the intended meaning - that
potatoes are now the fourth most important crop worldwide after wheat, rice, and corn. Moreover, the sentence formed by Option D uses the phrase "an even larger share", conveying the intended meaning - that potatoes are expected to supply a share of the world's nutritional requirements
that is even larger than the share they supplied before. Further, Option D avoids the grammatical construction error seen in Option B, as it does not use a pair of commas.
E: This answer choice incorrectly uses "Now the fourth most important crop worldwide after wheat, rice, and corn" to modify "expectations", illogically implying that
expectations are now the fourth most important crop worldwide after wheat, rice, and corn; the intended meaning is that
potatoes are now the fourth most important crop worldwide after wheat, rice, and corn; remember, in a “phrase + comma + noun” construction, the phrase must correctly modify the noun. Moreover, the sentence formed by Option E alters the meaning of the sentence through the phrase "even a larger share"; the construction of this phrase incorrectly implies that potatoes are expected to supply a larger share of the world's nutritional requirements,
in addition to something else; the intended meaning is that potatoes are expected to supply a share of the world's nutritional requirements
that is even larger than the share they supplied before.
Hence, D is the best answer choice.To understand the concept of "Phrase Comma Subject" and "Subject Comma Phrase" on GMAT, you may want to watch the following video (~1 minute):
To understand the concept of "Extra Information Between Commas" on GMAT, you may want to watch the following video (~4 minute):
To understand the concept of "Comma Splices and Run-Ons" on GMAT, you may want to watch the following video (~5 minutes):
All the best!
Experts' Global Team