首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
In the past oysters were raised in much the same way as dirt farmers raised tomatoes— by transplanting them. First, farmers sele
In the past oysters were raised in much the same way as dirt farmers raised tomatoes— by transplanting them. First, farmers sele
admin
2016-06-22
26
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 remains, 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(贝卵). 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 delicious 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 1900s marine biologists realized that if new measures were not taken, oysters would become extinct or at best a 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(顽强地)kept at it. Finally, in the 1940s a significant breakthrough was made.
The marine biologists discovered that by raising the temperature of the water, they could induce oysters to lay eggs 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(盐分)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
从文中的内容推知,海洋生物学家经过多次失败后,仍顽强地坚持了下来。终于,在20世纪40年代,取得了一个重要的突破性进展。
转载请注明原文地址:https://kaotiyun.com/show/kgQi777K
0
在职申硕(同等学力)英语
相关试题推荐
ItistheinteractionAbetweenpeople,Bratherthantheeventsthatoccurintheirlives,thatCarethemainfocusDofsocialps
ChildrenintheUnitedStatesareexposedtomanyinfluences______thoseoftheirfamilies.
Courageouspeoplethinkquicklyandactwithouthesitation.
WhenapostofficehandlesAlargequantitiesofmaildaily,itisessentialthatmechanicalmethodsBareusedCtomaintainprodu
Ourbodiesarewonderfullyskillfulatmaintainingbalance.Whenthetemperaturejumps,wesweattocooldown.Whenourbloodpr
Insomeways,theUnitedStateshasmadespectacularprogress.Firesnolongerdestroy18,000buildingsastheydidintheGreat
We(cannothardly)expectadolescents(tohaverespect)forthepossessionsofothers(if)theyhavenohopeofattaininganyof
Thereis(fewevidence)thatchildren(inlanguageclassrooms)learnforeignlanguages(anybetter)thanadultsinsimilar(clas
Thefollowingaccountbytheauthor______thedifferencebetweenEuropeanandAmericanreactions.
Wehavearesponsibilitytoensureournation’scontinuedprosperityandthemostsensiblewaytodothisisbyinvestmentinba
随机试题
心理学家认为,自卑感起源于人在幼年时期由于无能而产生的不胜任和痛苦的感觉。产生自卑感的原因有()
在Word2010中,下列关于页眉、页脚的叙述,错误的是()
心室肌细胞平台期的主要跨膜离子流是
施工平面布置图的设计原则有()。
个人汽车贷款的借款人需要调整借款期限的前提条件不包括()
银行业从业人员不允许有任何礼物收送的行为。()
已知a,b为实数,i是虚数单位.若(a一2i)i=b一i,则a2+b2=[].
在窗体上画一个文本框(名称为Text1)和一个标签(名称为Label1),程序运行后,在文本框中每输入一个字符,都会立即在标签中显示文本框中字符的个数。以下可以实现上述操作的事件过程是( )。
对于长度为n的线性表,若进行顺序查找,则时间复杂度为【】。
A、Theywillfeelannoyed.B、Theywillbesurprised.C、Theywillfeelintimated.D、Theywillbeimpressedbythem.D
最新回复
(
0
)