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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  78
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, which of the following is NOT mentioned as a stage of an oyster’s life?
选项 A、Debris.
B、Egg.
C、Larvae.
D、Spat.
答案A
解析 细节题。文章首段介绍了养殖牡蛎的过程，首先要清除苗床的陈旧贝壳及其他残余碎块，就是“debris"。因此A选项不能算是牡蛎生长的过程。选项B意思是“卵”，选项C意思是“幼虫”，选项D意思是“蚝卵”，都是牡蛎的生长过程的一个阶段，故选A。
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