2. 外语
  3. Changes in climate that had already taken place are manifested (1)______ from the decrease in extent and thickness of Arctic sea

Changes in climate that had already taken place are manifested (1)______ from the decrease in extent and thickness of Arctic sea

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问题     Changes in climate that had already taken place are manifested (1)______
from the decrease in extent and thickness of Arctic sea ice, permafrost thaw- (2)______
ing, coastal erosion, changes in ice sheets and ice shelves, altered distribu- (3)______
tion and abundance of species.
    Nowadays snows melt earlier in the springtime. Lakes, rivers and bogs
freeze much more later in the autumn. Reindeer herding becomes more (4)______
difficult so the ice is weak and may give way. Nowadays the winters are (5)______
much colder than they used to be. Occasionally during winter time it rains. (6)______
We never expected this; we could not be ready for this. It is very strange...
The cycle of the yearly calendar has been disturbed greatly. Warming over
northern land areas has been very greater than elsewhere in the world. The (7)______
changes are due to human modification of the concentration of greenhouse
gases during the 20th century, leading quite directly to the projections the (8)______
Arctic will warm by several times as much during the 21st century as it did
during the 20th century. The amplified warming in Arctic, in turn, directly (9)______
contributes to overall global warming, as well as cause changes that create (10)______
impacts over the rest of the globe.
(1)
选项
答案had — have
解析 使用过去完成体，必须有上下文或语境表明这个动作或状态发生在过去某个时间点以前。而这里上下文并没有提供这样一个过去的时间点，所以用过去完成体是不合适的。
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