2. 外语
  3. Dinosaurs, saber-tooth tigers and the dodo bird are famous examples of (1)______ animals that have become extinct. In case of th

Dinosaurs, saber-tooth tigers and the dodo bird are famous examples of (1)______ animals that have become extinct. In case of th

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问题     Dinosaurs, saber-tooth tigers and the dodo bird are famous examples of (1)______
animals that have become extinct. In case of the dinosaurs, it seems likely (2)______
that a catastrophic event alters the global climate enough to lead to their dis- (3)______ appearance. More recent extinctions and near-extinctions—such as the blue
whales, tiger, panda, and North American bison—have been the direct result (4)______
of human activity. By the early 1990s, species were becoming extinct at a
rate of three per hour, or 27,000 every year—a figure quoted by the Ameri
can biologist Edward O. Wilson of Harvard University, based on his most
conservative estimates. This rate of extinctions carries with it some terrible
consequences. Each plant that becomes extinct, for example, may take with
it as much as 30 insects and animals that depend on it for food. Habitat loss (5)______
is one of the most important causes of extinction. For rising populations in (6)______
many countries lead to the clearing of more land, habitats such as raining (7)______
forests and grasslands disappear.
    In the East Africa, once renowned for its wildlife, few wild animals re- (8)______
main living outside the boundaries of national parks and game reserves. In (9)______
other parts of the world, coastal ecosystems are clearing for development. (10)______
Wetland areas are drying out as a result of water extraction to support farm
ing and tourism. Bird species are among the worst affected by the loss of
wetlands.
(3)
选项
答案alters — altered
解析 这里谈的是恐龙灭绝的时期，所以时间是过去。
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