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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!
According to the passage，which of the following words best describes the efforts of the marine biologists working with oysters?
选项 A、Persistent.
B、Intermittent.
C、Traditional．
D、Fruitless.
答案A
解析 细节题。选项A意思是“坚持不懈，持之以恒”，选项B意思是“间歇的，断断续续的”，选项C意思是“传 统”，选项D意思是“无结果的，不成功的”。在文中第三段，倒数第二句They failed，but they doggedly kept at it. (他们失败了，但是他们依然顽强地坚持。)句中用以形容海产学家努力的词是“doggedly”，意为“坚持不懈地”，与选项A中的Persistent意思相近。因此选择A。
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大学英语四级

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