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  3. Long before Man lived on the Earth, there were fishes, reptiles, birds, insects, and some mammals. Although some of these animal

Long before Man lived on the Earth, there were fishes, reptiles, birds, insects, and some mammals. Although some of these animal

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问题     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.【B1】________
    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. That 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.
    【B2】______________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.
    【B3】________________There were also crablike 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.
    【B4】________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.
    【B5】________
    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, was 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 creature. 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 starfishes, 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.
【B4】
选项
答案A
解析 本题可以组合运用举例定位法、总分结构法和复现结构定位法。在第4题之后，我们注意到出现了一个明显表示举例的标志词of these(在这些之中)，这就意味着后面会出现一个具体的例子，而of these之前的第4题中的信息是包含和概括此例的一类事物，理解了of these前后两部分信息之间的这种关系，此题就很容易了。of these后面的例子是一种被称为ammonites的生物，而这种生物最大的特点是有shell(外壳)。所以就可以判断出of these之前的第4题的信息要概括出包含ammonites在内的一类生物，而此类生物的一个共同的特点就是也要有shell。同时，从文章结构的角度来看，本文采用了典型的总分结构，即第4题要填入一个总述句，这个总述句在段首的位置直接概括出“一类有外壳的生物”，即这个总述句中同时要出现shell的复现信息点。通过分析可以定位在选项A)The shellfish have a long history in the rock and many different kinds are known．(带壳鱼类在化石中有很长的历史，并且人们已经了解了很多不同的种类。)它可以和第4题之后的内容(Of these，有一种被称为ammonites的生物，这种生物最大的特点是有shell)相衔接。
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