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bolstered, fortified The second half of this sentence is not relevant to the blank. All you need to notice is the contrast between “warming” and “record low temperatures,” as well as the signal word “While.” Clearly, record low temperatures would not help an argument about global warming. A good fill-in would be helped. Subverted (undermined, in terms of power or authority) and subordinated (made inferior or subservient) are an incorrect pair. Defined (described exactly) and supplanted (replaced, substituted for) have no relationship.