GMAT Sentence Correction (SC) | Re: World War II taught the United States the folly of punishing a vanquis

Hi,

The answer is (D).

Here is the completeExplanation

Choice (A) is incorrect. Since United States is denoting the collective country, it is singular and therefore cannot be correctly referred to by the plural pronoun they.
Choice (B) is not technically incorrect, but it lacks precision since it does not state who enacted the Marshall Plan. Further, it uses a passive construction: “was enacted.”
Choice (C)
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