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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 selec

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

admin2012-05-17  54
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 little 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!
In the passage, the author mentions that the new strains of oyster are______.
选项 A、cheaper
B、shaped differently
C、better textured
D、healthier
答案D
解析 推理判断题。从文章最后一段第三句Going still further，they succeeded in breeding new strains that were resistant to diseases(并且还培育了新品种，这种新品种可以抵抗病害)可以得出线索，resistant to diseases与选项D属同一语义范畴，选项A的意思是“更便宜”．选项B的意思是“外形不同”，选项C的意思是“更漂亮的纹理”文中均未涉及。因此选择D。
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