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
外语
Bacteria are microscopic organisms which live on the surface of objects. They are one of the most ancient living things, which e
Bacteria are microscopic organisms which live on the surface of objects. They are one of the most ancient living things, which e
admin
2011-04-05
29
问题
Bacteria are microscopic organisms which live on the surface of objects. They are one of the most ancient living things, which exist on this planet for nearly 4,000 million years. Do you know the size of bacteria? It can only be measured in microns. Maybe you have not a standard in your mind how long a micron is. One micron is a thousandth of a millimeter, which equals about the diameter of a pinhead. Therefore, even if we enlarged the rounded bacterium a thousand times, it would only be the size of a pinhead. We barely see bacteria by a magnification an ordinary microscope of 100 times, even if we try, we cannot make out anything of their structure. There are normally millions of them together, for they can multiply really fast.
Scientists have found that some bacteria have attached to wavy-looking "hairs" called flagella. The flagella rotate, pushing the bacteria through the water. Others can glide along over surfaces by some little-understood mechanism. Bacteria are so small that they are influenced by the movements of the chemical molecules around them. They are active all the time. Even the bacteria without flagella often bound about in the water. They are pushed here and there, colliding with the watery molecules.
Bacteria cannot be detected because they don’t produce bad odor or change the color or texture of the food. Therefore, when people eat the food with many bacteria, they are likely to get hepatitis A, acute gastroenteritis and a host of other illnesses. Many households have refrigerators to prevent from bacteria. Of course, freezing food slows or stops the growth of bacteria, however, when food is thawed, the bacteria will become reactivated. Bacteria can not be totally destroyed before the food is thoroughly cooked. We need to know that not all bacteria are in connection with illness. Just some bacteria can cause disease. They are called pathogenic bacteria. Fortunately our immune system can protect us from them.
Bacteria are prokaryotes (single cells that do not contain a nucleus). It may seem weird to classify organisms according to such details, but with or without a nucleus is not trivial at all. The division between prokaryotes and eukaryotes (all organisms with a nucleus inside their cells) is of extreme importance in biology, and is the result of a major evolutionary breakthrough. Visit our program tomorrow if you want to know more, thank you.
What can be inferred from the last paragraph?
选项
A、Whether or not to have a nucleus is important in biology.
B、The speaker will tell us how to distinguish bacteria tomorrow.
C、Evolution will be the main topic, of the program next time.
D、Eukaryotes develop from prokaryotes.
答案
C
解析
根据最后一段第二句It may…“but with or without a nucleus is not trivial at all.”以及第三句“The division between prokaryotes and eukaryotes…is of extreme importance in biology.”可见,是否有细胞核这种区分对于生物学是很重要的,A项直接体现了文意,而不是推断出来的,故不选。根据该段倒数第二句“The division between prokaryotes…and is the result of a major evolutionary breakthrough.”可以推断出,明天的节目很可能会接着讨论进化问题,D项原文没有涉及,故正确答案为C选项。
转载请注明原文地址:https://kaotiyun.com/show/WTxd777K
本试题收录于:
公共英语四级笔试题库公共英语(PETS)分类
0
公共英语四级笔试
公共英语(PETS)
相关试题推荐
Thiskindofcomplexmeaningexpressedinwrittenlanguagesoonbecomesafishoutofwater.Thecomplexityofspokenlanguagei
Thiskindofcomplexmeaningexpressedinwrittenlanguagesoonbecomesafishoutofwater.Thecomplexityofspokenlanguagei
ApersonbecomespartoftheChristiancommunitythroughbaptism--itisamatterofchoice【C1】______birth.TheChristiancommun
ThechangingprofileofacityintheUnitedStatesisapparentintheshiftingdefinitionsusedbytheUnitedStatesBureauof
Societywasfascinatedbyscienceandthingsscientificinthenineteenthcentury.Greatbreakthroughsinengineering,theuseo
Aspearorarobothasthequalityoftechnologyonlywhenit______.
Usuallypeoplecan’tfeelthechangeofthesociety.Fromgenerationtogenerationweliveinthesameframeoffamilyandstruc
Whycan’tthelibraryissuelibrarycardstoeveryonewhoapplies?
1897细节题。根据“In1897,thelibrarymovedintoitsownbuildingacrossthestreetfromthe
随机试题
蛋白质在小肠中最终分解为________。
A、按效价单位计B、按干燥品重量计C、根据数值的有效数位来确定D、按百万分之几计E、按百分含量计杂质铁盐的限量( )。
工程量清单计价模式下,关于分部分项工程量和定额子目的说法,错误的是()。
下列不属于明代戏曲“四大声腔”的是()
单位要进行一次座位调整,有1/3的座位靠窗,你是牵头人,你怎么把事情办好?
1919年,《新青年》杂志发表()撰写的《我的马克思主义观》一文,该文章系统地介绍了马克思主义唯物史观、政治经济学和科学社会主义的基本原理。
【四时捺钵】延安大学2011年中国古代史复试真题;内蒙古大学2015年中国史真题;北京大学2017年历史学基础(中国史)真题
Exhibitionhall
已知y=y(x)是微分方程(x2+y2)dy=dx—dy的任意解,并在y=y(x)的定义域内取x0,记y0=y(x0).(1)证明:;(2)证明:均存在.
Lookatthenotesbelow.Someinformationismissing.Youwillhearadialogueonjobinterviewandconcludemainpoints.Forea
最新回复
(
0
)