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题库 / GMATLA-RC-275
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 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) 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 that would dominate the marine ecosystems of the area for the next 215 million years. 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. And, in fact, there is evidence of major ecological and geological changes during this period: the sea level dropped drastically and mountain ranges were formed, in this instance, rather than leading to large-scale extinctions, these kinds of environmental changes may have resulted in an enriched pattern of habitats and nutrients, which in turn gave rise to the Ordovician radiation, However, the actual relationship between these environmental factors and the diversification of life forms is not yet fully understood
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
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正确答案是 B。原文指出，虽然放射期长达数千万年，但 major changes 发生在一个地质上很短的时间跨度内，而且似乎发生在全世界范围内，这表明外部事件是这种放射的主要因素。在那段时期，海面下降得非常厉害，山脉也形成了，而这种环境变化不会导致大范围的灭绝，相反，这可能会导致更加富饶的栖息地和养分，从而带来奥多维斯期的放射。因此可以推断，在奥多维斯期的地质变化可能会创造条件有利于许多新的生命形式的进化。因此，选项 B 才是正确答案。
d 选项为什么不对啊
我觉得可能是因为文中没有提及是both可以i陆生和水生？
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D算是B的一个衍生，若D正确，B必正确。
且文章未提到 new species adapted to living both on land and in water。
因此选B
错选了D。但是其实跟D相比，B要更准确严谨。考试的时候一定要记得！！
radiations (periods when existing life-forms gave rise to variations that would eventually evolve into entirely new species) 有解释的，不要想当然以为是“辐射”。QAQ
直接细节题： in this instance, rather than leading to large-scale extinctions, these kinds of environmental changes may have resulted in an enriched pattern of habitats and nutrients, which in turn gave rise to the Ordovician radiation
there is evidence of major ecological and geological changes during this period: the sea level dropped drastically and mountain ranges were formed, in this instance, rather than leading to large-scale extinctions, these kinds of environmental changes may have resulted in an enriched pattern of habitats and nutrients, which in turn gave rise to the Ordovician radiation
This rock record provides clues about one of the most significant radiations (periods when existing life-forms gave rise to variations that would eventually) evolve into entirely new species) in the history of marine invertebrates.