Boreal forest is at the southern boundary of the moss-dominated tundra, which remains characteristically treeless because its spongy surface retains water that cannot drain away through the underlying permafrost. But as temperatures rise the permafrost recedes, (i)______ the (ii)______ of forest.
2 、GRE考試容易出現一些熟詞僻義的考點，很多單詞可能辭彙書都不會收錄，但是卻能成為考點。
例如辭彙書基本不收錄的單詞usage這個詞，在GRE考試中就考到過「對待方式」這種生僻的意思。
填空-例2【巍哥GRE填空1200題section32第1題】
With the numerous opponents of the controversial new taxation measure in such a fury, anyone who publicly advocated the measure did not fail to meet with _____ usage.
Caricature can be revealing as well as amusing, and Ager』s novel is both: Ager』s delineation of class, ethnic, and generational struggle is exaggerated for comical effect, but it _____ nonetheless.
