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 Bacteria are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size
Bacteria Bacteria are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size
admin
2011-01-05
66
问题
Bacteria
Bacteria are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size is measured in microns. One micron is a thousand of a millimeter: a pinhead is about a millimeter across.
Rod-shaped bacteria are usually from two to four microns long, while rounded ones are generally one micron in diameter. Thus if you enlarged a rounded bacterium a thousand times, it would be just about the size of a pinhead. An adult human magnified by the same amount would be over a mile (1. 6 kilometers) tall. Even with an ordinary microscope, you must look closely to see bacteria. Using a magnification of 100 times, one finds that bacteria are barely visible as tiny rods or dots. One cannot make out anything of their structure. Using special stains, one can see that some bacteria have attached to them wavy-looking " hairs" called flagella. Others have only one flagellum. The flagella rotate, pushing the bacteria through the water. Many bacteria lack flagella and cannot move about by their own power, while others can glide along over surfaces by some little-understood mechanism.
From the bacterial point of view, the world is a very different place from what it is to humans. To a bacterium water is as thick as molasses is to us. Bacteria are so small that they are influenced by the movements of the chemical molecules around them. Bacteria under the microscope, even those with no flagella, often bounce about in the water. This is because they collide with the water molecules and are pushed this way and that. Molecules move so rapidly that within a tenth of a second the molecules around a bacterium have all been replaced by new ones; even bacteria without flagella are thus constantly exposed to a changing environment.
It’s hard to see bacteria clearly even with an ordinary microscope.
选项
A、Right
B、Wrong
C、Not mentioned
答案
A
解析
从第二段第四句话我们知道用一般的显微镜观察细菌时,必须仔细观察才能看见它们。因此本句表述是正确的。
转载请注明原文地址:https://kaotiyun.com/show/mlmd777K
本试题收录于:
职称英语卫生类A级题库职称英语分类
0
职称英语卫生类A级
职称英语
相关试题推荐
Youwillhearfivepeoplegivingtheiropinionsonchanginginlife.Forquestions9-13,choosefromthelistA~Fwhateach
Whatisthewritertryingtodointhetext?WhichofthefollowingbestdescribesElizabeth’sfeelingsaboutthetower?
•YouhavetowriteastoryforyourEnglishteacher.•Yourstorymustbeginwiththissentence:Iwasstandingbesidesomeone
Youwillhearsomeinformationaboutavisitortoaschool.Listenandcompletequestions21-25.Youwillheartheinformationt
Lastwinter,sheboughtapairofbeautifulboots.
Whydidmanywomenfeelthatknittingwasoutofdate?Theword"quit"inParagraph2isclosestinmeaningto
ThispoemdepictsthebeautifulsceneryofatownintheSouth.
WalkaQuarter-MileorDieIfyoucanwalkaquarter-mile,odds(可能性)areyouhaveatleastsixyearsoflifeleftinyou,s
WalkaQuarter-MileorDieIfyoucanwalkaquarter-mile,odds(可能性)areyouhaveatleastsixyearsoflifeleftinyou,s
Youmustshineyourshoes.
随机试题
简述怎样辩证对待人生矛盾。
新生女婴尿道长仅
若热象明显加有口苦心烦者加
抗酸染色后呈红色的细菌是()
对系统性红斑狼疮的诊断最特异的检查项目是
环境影响评价工程师在其职业资格登记有效期内接受继续教育的时间应累计不少于()。
因果预测分析法是指通过影响产品销售量(因变量)的相关因素(自变量)以及它们之间的函数关系,并利用这种函数关系进行产品销售预测的方法,因果预测分析法最常用的是()。
关于无形资产的摊销,下列会计处理正确的有()。
国际多式联运以__________为媒介,把海洋运输、铁路运输、公路运输、航空运输和内河运输等传统的单一运输方式有机地结合起来,采用__________综合利用,以完成国际问的运输任务。
下列关于WindowsServer2003系统下DNS服务器的描述中,错误的是()。
最新回复
(
0
)