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文章講解：

①Ecologists study how millions of species share the world, rather than take on the whole?planet at once; they generally focus on a single ecosystem, be it a prairie, a?tidal flat[劍1]?,or a sanddune?.?[劍3]??②Even within those limits, they are frustrated by?porous frontiers.?③As a result, ecologists have done some of their most important work on islands, nature’s own?isolated?laboratories, which may be colonized only a few times over the course of millions of years.[劍5]?④On them, ecologists have figured out how?the size of a given habitat determine how many species it can support.?⑤They have then applied that knowledge to the mainland, showing how fragmented ecosystems become like archipelagoes[劍7]?,where extinctions can strike.?

①事實(shí)

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② 事實(shí)/生態(tài)學(xué)家自己的觀點(diǎn)

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③

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④

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⑤

?[劍1]潮汐平原

?[劍7]?ɑrk?ˋp?l??go群島

1. It can be inferred that the term “porous frontiers” is used to refer to

單詞題變體

A. a tendency for the area of an ecosystem to shrink?沒(méi)有證據(jù)

B. human-caused processes that alter the character of an ecosystem?沒(méi)有證據(jù)

C. movement of species into an ecosystem from outside?符合

D. variation in what theterm “ecosystem” signifies?沒(méi)有證據(jù)

E. lack of protection for endangered habitats?沒(méi)有證據(jù)

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2. In the context in which itappears, “isolated” most nearly means

A. completely uncontaminated

B. somewhat unusual

C. extremely rare

D. relatively inaccessible?符合

E. strictly confined