Explanation

Buttress, as a noun or a verb, relates to support and is therefore justified by the clue “additional support.” None of the other choices relate to the text. Note that you certainly do not need to memorize architectural terms for the GRE, but you should definitely know the metaphorical meaning of buttress (to support), and the sentence provides the clue about “needed additional support,” so this question is fair game.

Buttress.
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Sandy
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