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
We don’t see or hear them, but every day they quietly go about their work--filtering and cleansing our rivers and streams. And i
We don’t see or hear them, but every day they quietly go about their work--filtering and cleansing our rivers and streams. And i
admin
2011-03-11
61
问题
We don’t see or hear them, but every day they quietly go about their work--filtering and cleansing our rivers and streams. And if we don’t act soon, they’ll disappear from the workforce just when we need them most. I am talking about pigtoes, monkeyface, pink heelsplitter and purple wartyback--freshwater mussels (贻贝) with funny names that belie the seriousness of their labors. (41) .
One mussel alone can cleanse as much as a gallon of water per hour. Add up the work of a whole mussel community, and you get a virtual water treatment plant. According to Ethan Nedeau, an expert on the freshwater mussels of New England, even half the population of mussels at work in a one-half mile segment of New Hampshire’s Ashuelot River can help cleanse more than 11.2 million gallons of water a day--roughly the quantity of household water used by 112 000 people.
(42) . Today 69 percent of US freshwater mussel species are to some degree at risk of extinction or already extinct. The most diverse assemblage of freshwater mussels ever known was located in the middle stretch of the Tennessee River in northern Alabama. Before the damming of the river in the early 1900s, 69 mussel species had been spotted in this reach; 32 of them have apparently disappeared, with no recording sightings in nearly a century.
(43) . Like many freshwater mussels, the orange-nacre mucket has a fascinating life cycle and exhibits some of the most sophisticated mimicry in the animal kingdom. The females essentially use their offspring to lure fish into helping them colonize new stream bottoms. They package their larvae (幼虫) at the end of jelly--like tubes that can extend eight feet out into the water. To fish swimming by, the larvae dancing in the riffles of the river current looks like a tasty minnow. When the fish bites, the tube breaks, releasing the larvae into the stream. A few of the offspring attach to the fish’s gills and hitchhike around with their firmed host for a week or two, absorbing nutrients and growing along the way. (44) .
Along with 16 other threatened or endangered mussel species in the Mobile watershed, the orange-nacre mucket is at risk of extinction--in large part due to excessive pollution and dams that have diminished the river habitat they need to survive. To me, the loss of such industrious, fascinating creatures diminishes more than our water quality-- it diminishes our natural heritage and our world.
(45) . So as we celebrate World Water Day, I hope we also celebrate the freshwater mussels that help keep our waters clean and healthy--and commit to efforts to conserve them.
[A] My favorite freshwater mussel is the orange-nacre mucket, found only in the rivers and streams of Alabama’s Mobile River basin.
[B] The United States ranks first in the world in the number of known species of freshwater mussels 292, com- pared with just 10 in all of Europe. But we’re losing these "living filters" all too fast.
[C] Only habitat improvements, in some cases combined with mussel breeding and release efforts, can save these and the other 200 freshwater mussel species at risk nationwide.
[D] Because I bet we’ll miss these little creatures with the whimsical names when they’re gone.
[E] They suck water in, filter out bits of algae, bacteria and other tiny particles, and then release it back to the river cleaner than before.
[F] Finally, the young mussels drop off, float to the river bottom, and colonize new territory--and before long begin their vital task of water purification.
[G] It is our responsibility to take actions to protect the freshwater mussels, otherwise they will disappear in the future and the water will not be refreshed.
选项
答案
B
解析
本句位于第三段开头,有提挈整段的作用。下文紧接着叙述美国淡水贻贝面临的问题。由此可知该段开头应该讲有关美国淡水贻贝的内容。所有选项中,只有[B]提及美国的情况,故[B]正确。
转载请注明原文地址:https://kaotiyun.com/show/z6p4777K
0
考研英语一
相关试题推荐
InthenineteenthcenturyCharlesDickens,theEnglishnovelist,wroteexcitedly(1)_____astage-coach,pulledalongbyateam
Writeanessayof160-200wordsbasedonthefollowingdrawing.Inyouressay,youshouldfirstdescribethedrawing,theninter
ReadthefollowingtextcarefullyandthentranslatetheunderlinedsegmentsintoChinese.Yourtranslationshouldbewrittencl
Therearecertainpeoplewhobehaveinaquitepeculiarfashionduringtheworkofanalysis.Whenonespeakshopefullytothemo
Inthefollowingtext,somesentenceshavebeenremoved.ForQuestions41-45,choosethemostsuitableonefromthelist(A、B、C、
Inthefollowingtext,somesentenceshavebeenremoved.ForQuestions41-45,choosethemostsuitableonefromthelist(A、B、C、
Writeanessayof160-200wordsbasedonthefollowingdrawing.Inyouressay,youshouldfirstdescribethedrawing,theninter
Theideaofpublicworksprojectsasadevicetopreventorcontroldepressionwasdesignedasameansofcreatingjobopportuni
Wedon’tseeorhearthem,buteverydaytheyquietlygoabouttheirwork--filteringandcleansingourriversandstreams.Andi
Wedon’tseeorhearthem,buteverydaytheyquietlygoabouttheirwork--filteringandcleansingourriversandstreams.Andi
随机试题
A、Hestudiedtheblueprintsofotherfamousbuildings.B、Heinquiredabouthisclient’sfamilybackground.C、Heobservedhiscli
美术学科核心素养中,()指从文化的角度观察和理解美术作品、美术现象和观念。
国际单位制中基本单位有7种。
“申报日期”栏应填()。“数量及单位”栏应填()。
等额本息还款法是指借款人每月以相等的金额偿还贷款本金,贷款利息随本金逐月递减,还款额逐月递减。()
企业薪酬调查分析报告的内容不包括()
根据所给资料,回答下列问题。2010年,我国黄金产量为340.88吨,同比增长8.57%。其中矿产金280.04吨,同比增长7.27%;有色副产金60.84吨,同比增长14.95%。2010年,我国黄金企业实现工业总产值2292.88亿
姜寨遗址是比较典型的()的村落遗址
A、 B、 C、 D、 B
算法的基本特征是可行性、确定性、【】和拥有足够的情报。
最新回复
(
0
)