2. 考研
  3. Directions:In the following text, some sentences have been removed. For Questions 41—45. choose the most suitable one from the l

Directions:In the following text, some sentences have been removed. For Questions 41—45. choose the most suitable one from the l

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问题 Directions:In the following text, some sentences have been removed. For Questions 41—45. choose the most suitable one from the list A—G to fit into each of the numbered blank. There are two extra choices, which do not fit in any of the gaps. Mark your answers on ANSWER SHEET 1.(10 points)
    Long before Man lived on the Earth, there were fishes, reptiles, birds, insects, and some mammals. Although some of these animals were ancestors of kinds living today, others are now extinct, that is, they have no descendants alive now. 【R1】______. Very occasionally the rocks show impression of skin, so that, apart from color, we can build up a reasonably accurate picture of an animal that died millions of years ago. The kind of rock in which the remains are found tells us much about the nature of the original land, often of the plants that grew on it, and even of its climate.
    【R2】______. Nearly all of the fossils that we know were preserved in rocks formed by water action, and most of these are of animals that lived in or near water. Thus it follows that there must be many kinds of mammals, birds, and insects of which we know nothing.
    【R3】______. There were also crab-like creatures, whose bodies were covered with a horny substance. The body segments each had two pairs of legs, one pair for walking on the sandy bottom, the other for swimming. The head was a kind of shield with a pair of compound eyes, often with thousands of lenses. They were usually an inch or two long but some were 2 feet.
    【R4】______. Of these, the ammonites are very interesting and important. They have a shell composed of many chambers, each representing a temporary home of the animal. As the young grew larger it grew a new chamber and sealed off the previous one. Thousands of these can be seen in the rocks on the Dorset Coast.
    【R5】______.
    About 75 million years ago the Age of Reptiles was over and most of the groups died out. The mammals quickly developed, and we can trace the evolution of many familiar animals such as the elephant and horse. Many of the later mammals, though now extinct, were known to primitive man and were featured by him in cave paintings and on bone carvings.
[A]The shellfish have a long history in the rock and many different kinds are known.
[B]Nevertheless, we know a great deal about many of them because their bones and shells have been preserved in the rocks as fossils. From them we can tell their size and shape, how they walked, the kind of food they ate.
[C]The first animals with true backbones were the fishes, first known in the rocks of 375 million years ago. About 300 million years ago the amphibians, the animals able to live both on land and in water, appeared. They were giant, sometimes 8 feet long, and many of them lived in the swampy pools in which our coal seam, or layer, formed. The amphibians gave rise to the reptiles and for nearly 150 million years these were the principal forms of life on land, in the sea, and in the air.
[D]The best index fossils tend to be marine creatures. These animals evolved rapidly and spread over large areas of the world.
[E]The earliest animals whose remains have been found were all very simple kinds and lived in the sea. Later forms are more complex, and among these are the sea-lilies, relations of the star-fishes, which had long arms and were attached by a long stalk to the sea bed, or to rocks.
[F]When an animal dies, the body, its bones, or shell, may often be carried away by streams into lakes or the sea and there get covered up by mud. If the animal lived in the sea its body would probably sink and be covered with mud. More and more mud would fall upon it until the bones or shell become embedded and preserved.
[G]Many factors can influence how fossils are preserved in rocks. Remains of an organism may be replaced by minerals, dissolved by an acidic solution to leave only their impression, or simply reduced to a more stable form.
【R2】
选项
答案F
解析 本题中的空格出现在第二段段首，既可能是第二段的主题句，也可能是第一段内容与空格后面内容的衔接部分，与上文有一定的连贯性，又与下文中的重点提示信息相关联。上文谈到岩石有利于人类了解已灭绝的动物，下文大意是由于动物化石是通过水流作用而保存下来的，因此存在过许多人类尚未知晓的非水生或亲水动物。其中提到的新的关键信息是water action。最大的干扰项是[G]，因为它一开始就有和该段相同的内容fossils are preserved。但是该选项的内容是指出很多因素都会影响化石的保存，即：有机物的残骸可能被矿物所替代，接着被酸性溶液所溶解，只留下残骸的印记，或者只是还原到一种更稳定的形态。显然这些内容与下文毫无关联。只有[F]提到动物的尸体都会被冲到湖泊或海洋形成化石，其中carried away by streams…covered up hy mud就是wa—ter action，因此足正确选项。此题难度较大，可以采取先解答其他题的策略。
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