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  3. In the past oysters were raised in much the same way as dirt farmers raised tomatoes-by transplanting them．First，farmers selecte

In the past oysters were raised in much the same way as dirt farmers raised tomatoes-by transplanting them．First，farmers selecte

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问题     In the past oysters were raised in much the same way as dirt farmers raised tomatoes-by transplanting them．First，farmers selected the oyster bed，cleared the bottom of old shells and other debris，and then scattered clean shells about．Next they “planted”fertilized oyster eggs，which within two or three weeks hatched into larvae.The larvae drifted until they attached themselves to the clean shells on the bottom．There they remained and in time grew into baby oysters called seed or spat．The spat grew larger by drawing in seawater from which they derived microscopic particles of food．Before long，farmers gathered the baby oysters，transplanted them in other waters to speed up their growth，and then transplanted them once more into another body of water to fatten them up。
    Until recently the supply of wild oysters and those crudely farmed were more than enough to satisfy people’s needs．But today the delectable seafood is no longer available in abundance．The problem has become so serious that some oyster beds have vanished entirely。
    Fortunately，as far back as the early 1900’s marine biologists realized that if new measures were not taken，oysters would become extinct or at least luxury food．So they set up well equipped hatcheries and went to work．But they did not have the proper equipment or the skill to handle the eggs．They did not know when，what，and how to feed the larvae．And they knew 1ittle about the predators that attacked and ate baby oysters by the millions．They failed，but they doggedly kept at it．Finally，in the 1940’s a significant breakthrough was made．
    The marine biologists discovered that by raising the temperature of the water，they could induce oysters to spawn not only in the summer but also in the fall，winter，and spring。Later they developed a technique for feeding the larvae and rearing them to spat．Going still further，they succeeded in breeding new strains that were resistant to diseases，grew faster and larger，and flourished in water of different salinities and temperatures．In addition，the cultivated oysters tasted better!
Which of the following would be the best title for the passage?
选项 A、The Threatened Extinction of Marine Life．
B、The Cultivation of Oysters.
C、The Discoveries Made by Marine Biologists.
D、The Varieties of Wild Oysters．
答案B
解析 主旨题。文章介绍了人工养殖牡蛎的过程、方法及遇到的问题等。因此B答案全面概括了全文大意。A选项是说海洋生物受到灭绝的威胁，C选项是说海产生物专家的发现。选项A和C分别概括了第二段和第三段的大意，以偏概全，故排除。D选项是说野生牡蛎的不同种类，文中并无涉及。故选B。
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大学英语四级

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