The dry mountain ranges of the
Western united states contain rocks
dating back 440 to 510 million years,
Line to the Ordovician period, and teeming
5) with evidence of tropical marine life.
This rock record provides clues about
one of the most significant radiations
(periods when existing life-forms gave
rise to variations that would eventually)
10) evolve into entirely new species) in the
history of marine invertebrates. During
this radiation the number of marine
biological families increased greatly,
and these families included species
15) that would dominate the marine ecosys-
tems of the area for the next 215 million
years. Although the radiation span-
ned tens of millions of years, major
changes in many species occurred
20) during a geologically short time span
within the radiation and, furthermore,
appear to have occurred worldwide,
suggesting that external events were
major factors in the radiation. And , in
25) fact, there is evidence of major eco-
logical and geological changes during
this period: the sea level dropped
drastically and mountain ranges were
formed, in this instance, rather than
30) leading to large-scale extinctions,
these kinds of environmental changes
may have resulted in an enriched pat-
tem of habitats and nutrients, which in
turn gave rise to the Ordovician radi-
35) ation, However, the actual relationship
between these environmental factors
and the diversification of life forms is
not yet fully understood
-------------------------------------------------------------------------------------------------------
文章概况：文章开始就说有一个地方包含了一些石头，这些石头能证明这里曾经有海洋生物，中间论证的这些石头包含了哪些证据（好像和辐射有点关系），结尾说文章所探讨的这些石头中所包含的环境因素和生命之间的关系现在还不能被完全理解。
20.
The passage is primarily concerned with
evaluating the evidence of a major geo
logic period and determining its duration
describing an evolutionary phenomenon
and speculating about its cause
explaining the mechanisms through which
marine life-forms evolved during a par
ticular period
analyzing the impact on later life-forms of
an important evolutionary development
contrasting a period of evolutionary
change with other such periods
-------------------------------------------------------------------------------------------------
问主旨，我们直接看选项A 围绕着地址时期谈的，主体不对杀。B描述一个现象，并探讨其原因，有点关系，留着。C 解释生命进化的一种机制，即使留着这个选项也没有B犯错可能性小。D 分析了一个进化对于后期的生命形式的影响，文章没有围绕影响谈过，杀。E对比了1个生命进化和另一个，没说过这个比较，杀。
21.
Which of the following can be inferred from
the passage regarding the geologic changes
that occurred during Ordovician period?
They were more drastic than those
associated with other radiations
They may have created conditions
favorable to the evolution of many
new life-forms
They may have caused the extinction
of many of the marine species living
in shallow waters
They may have been a factor in the
development of new species adapted
to living both on land and in water .
They hastened the formation of the
extensive dry regions found in the
western united states
-----------------------------------------------------------------------------------------------
问的是一个细节，根据题干中的词汇（应该根据geologic changes定位， Ordovician period对于定位没有用，这个词是文章的核心概念）我们应该可以定位到原文这句话： Although the radiation spanned tens of millions of years, major changes in many species occurred during a geologically short time span within the radiation and, furthermore, appear to have occurred worldwide,suggesting that external events were major factors in the radiation.大概意思是生物一些主要变化在一段较短的时间里发生，而外部因素是一些主要因素，我们来看选项
A 说更加drastic，没说过，杀
B 创造了一些条件导致生命形式，说生命形式了，和文章信息有关系，留着。
C 导致海洋生物灭绝，文章没说了灭绝，杀
D 一个新物种既适应土地又适应海洋生活的因素，没说，杀
E 加速了干燥地区形成，没提，杀。
22.
Which of the following best describes the
function of last sentence of the passage ?
it points out that the events described
in the passage may be atypical
it alludes to the fact that there is dis
agreement in the scientific community
over the importance of the Ordovician
radiation
it concludes that the evidence presented
in the passage is insufficient to support
the proposed hypothesis because it
comes from a limited geographic area
it warns the reader against seeing a
connection between the biological
and geolgic changes described in
the passage
it alerts the reader that current knowledge
cannot completely explain the relationship
suggested by the evidence presented
问最后一句话的功能。说环境和生命之间的关系现在还不清楚，我们来看选项。A 指出了文章描述的事件是不是典型的，没说是否是典型的，杀。B还说agreement，和那句话方向都是反着的，杀C because后半部分内容说的很扯，杀。D说警告读者不要看出两者之间的关系，杀，很搞笑的一个选项。E说提醒读者现有知识还不能解释文章提出的那个关系，和我读到的信息令人发指的对应，留着。
