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 are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size is measured
Bacteria are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size is measured
admin
2021-11-11
9
问题
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 thousandth of a millimeter; a pinhead is about a millimeter across. Rod-shaped bacteria are usually 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 (鞭毛). 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 (分子) 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 Molecules move so rapidly that within a tenth of a second the molecules around a bacterium have all been replaced by new ones.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.
According to the passage, one who examines bacteria with an ordinary microscope, using a magnification of 100 times will see________.
选项
A、tiny rods
B、stains
C、wavy-looking hairs
D、detailed structures
答案
A
解析
根据文中第二段前两句“Using a magnification of 100 times,one finds that bacteria are barely visible as tiny rods or dots”,故选A。
转载请注明原文地址:https://kaotiyun.com/show/Z8RC777K
本试题收录于:
英语题库普高专升本分类
0
英语
普高专升本
相关试题推荐
Wefindthatbrightchildrenarerarelyheldbackbymixed-abilityteaching.Onthecontrary,boththeirknowledgeandexperienc
Ofallthefamilymembers,grandparentsareprobablytheleastvalued.Theyarejustthepeoplewhohavealwaysbeenaround.The
Thereisapopularbeliefamongparentsthatschoolsarenolongerinterestedinspelling.NoschoolIhavetaughtinhaseveri
Thispartistotestyourabilitytodopracticalwriting.Youarerequiredtowritealetterofinvitation.Youcanrefertoth
【T1】Whentheyoungmanstartstoearnhisownliving,hebecomesfreefromthedisciplineofschoolandparents:butatthesame
【T1】Whentheyoungmanstartstoearnhisownliving,hebecomesfreefromthedisciplineofschoolandparents:butatthesame
weexcelatmakingalivingbutoftenfailinmakingalife.
Themoreexerciseyoutake,thelesslikelyyoucatchacold.
尽管他的建议听起来挺好的,但我认为在目前阶段既不现实也行不通。
A.他们在辩论中表现非常出色,我们很难不佩服他们。B.如果你想申请一份学生签证,你就必须填写1M2A表格,你可以在最近的提供签证服务的英国领事馆免费获得该表格。C.医院内,在可能干扰设备使用的任何区域,禁止使用手机。D.众所周知,我们的许多问题一
随机试题
分析问题并找出问题中主要矛盾的过程是处于问题解决阶段的( )。
患者发热、咳嗽、咳痰,血压80/50mmHg,临床诊断为中毒性肺炎。首选以下哪项处理
证券市场监管原则中,()要求证券市场具有充分的透明度,要实现市场信息的公开化。
人力资本论是华勒提出的。
古典乐派的代表人物有巴赫、亨德尔、贝多芬、海顿、莫扎特。()
"Ifwintercomes,canspringbefarbehind?"isfromShelly’s______.
我国教育目的建立的理论基础是()。
当螃蟹放到不高的水池里时,单个螃蟹可能凭着自己的本事爬出来,但是如果有好几个螃蟹,它们就会叠罗汉,总有一个在上边,一个在下边,这时底下的那个就不干了,拼命爬出来,并且开始拉上面螃蟹的腿,结果谁也爬不高。这就是螃蟹文化。螃蟹之间的互相制约的文化,核心就是共同
实际工作中的教条主义和经验主义的错误在于
Theyshouldadoptamore_____approachandinvestigatealternativeusesfortheirproperty.
最新回复
(
0
)