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
专升本
Bacteria(细菌) are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size is measu
Bacteria(细菌) are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size is measu
admin
2018-04-17
33
问题
Bacteria(细菌) 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 thousandth 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 (糖蜜) 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this way and that molecules move so rapidly that within a tenth of a second the molecules around a flagellum have been replaced by new ones. Even bacteria without flagella are thus constantly exposed to a changing environment.
According to the passage, someone who examines bacteria using only a microscope that magnifies 100 times would see______.
选项
A、tiny dots
B、small "hairs"
C、large rods
D、detailed structures
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/fKiC777K
本试题收录于:
英语题库成考专升本分类
0
英语
成考专升本
相关试题推荐
Whenallthepeoplehadassembled,theking,surroundedbyhiscourt,【C1】______asignal.Thenadoorbeneathhimopened,andt
Thereislittlewecandoaboutit,_____?
Theyarebusy______intheirlessonsbeforetheexam.
Animportantbusinessmanwasaskedtogiveatwenty-minutespeechinanothercity.Hewastoobusytowriteithimself,soheas
______inanatmosphereofsimplelivingwaswhatherparentswishedfor.
PeopleinBritainarelivinglongerandare【56】,【57】moreandmoremoneyisbeingspentonconsumergoods,【58】thelateststati
I____asleepbecauseittookmealongtimetorealizethatthetelephonewasringing.
W:Boy,howquicklytechnologychanges!Somanypeoplehaveacomputerintheirhomenowadays.M:______
FrankLloydWrightprobablyisthegreatestarchitectthattheUnitedStateshaseverproduced.Hewasvery【21】andhadanatural
随机试题
某社会工作服务机构通过参加公益创投,从本地民政局获得50万元资金支持,用于为社区独居老人提供服务。依据社会服务机构筹资方法分类,该机构获得资金的方式属于()。
患者,男性,30岁,持续发热2周住院。查体:T39.5℃,巩膜轻度黄染,肝、脾肋下1cm。血常规:WBC4×109/L,总胆红素98μmoWL,ALT80U/L,肥达反应“O”1:80,“H”1:160。该患者最可能的诊断是
患者,女,25岁。妊娠8周,下列除哪组药外,均不宜服用()
下列哪一项不属于公安法制工作?()
一群艺术历史学家要确定某些近期发现的原稿的创作时间,每一幅画都是由不同的画家创作的。这些历史学家请了一位化学家来测试这些画上6种颜料出现的时间。现已经知道这些颜料第一次被生产的时间,并且还知道某些颜料停止生产的使用的时间,如下所示:颜料1:公元1
马克思主义经典作家关于人的全面发展的基本涵义是()。
利用高速通信网络将多台高性能工作站或微型机互连构成集群系统,其系统结构形式属于(6)计算机。
常见的软件开发模型有瀑布模型、演化模型、螺旋模型、喷泉模型等。其中(5)模型适用于需求明确或很少变更的项目,(6)模型主要用来描述面向对象的软件开发过程。
Icanhardlybelieveit,it’samazing.
Syntacticmovementisdictatedbyrulestraditionallycalled______.
最新回复
(
0
)