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
Thousands of years ago man used handy rocks for his surgical operations. Later he used sharp bones or horns, metal knives and mo
Thousands of years ago man used handy rocks for his surgical operations. Later he used sharp bones or horns, metal knives and mo
admin
2016-12-05
48
问题
Thousands of years ago man used handy rocks for his surgical operations. Later he used sharp bones or horns, metal knives and more recently, rubber and plastic. In the 1960s a new tool was developed, one which was, first of all, to be of great practical use to the armed forces and industry, but which was also to revolutionize the art and science of surgery.
The tool is the laser and it is being used by more and more surgeons all over the world. As we all know, light is hot, and any source of light will give warmth. But light is usually spread out over a wide area. The light in a laser beam, however, is concentrated. This means that a light with no more power than that produced by an ordinary electric light bulb becomes intensely strong as it is concentrated to a pinpoint-sized beam.
Experiments with these pinpoint beams showed researchers that different energy sources produce beams that have a particular effect on certain living cells. It is now possible for eye surgeons to operate on the back of human eye without harming the front of the eye, simply by passing a laser beam right through the eye-ball. Operations which once left patients exhausted and in need of long period of recovery time now leave them feeling relaxed and comfortable.
The rapid development of laser techniques in the past ten years has made it clear that the future is likely to be very exciting. Perhaps some cancers will be treated with laser in a way that makes surgery not only safer but also more effective.
The reason why the laser beam is very strong is that________.
选项
A、it is artificially illuminated
B、it is made up of a concentrated beam of light
C、it sends out heat in all directions
D、its heat is increased by the heat of the sun
答案
B
解析
事实细节题。题干的意思是“为什么激光束的能量比较强?”根据原文第二段最后一句可知“能量被集中到一起而变得强大”。故答案为B。
转载请注明原文地址:https://jikaoti.com/ti/qHVsFFFM
本试题收录于:
公共英语二级笔试题库公共英语(PETS)分类
0
公共英语二级笔试
公共英语(PETS)
相关试题推荐
LONDON—LifeforCathyHangerandherthreechildrenissettopermanent(永久的)fast-forward.Theirfullschooldayandherj
Formanypeopletoday,readingisnolongerrelaxation.Tokeepuptheirworktheymustreadletters,reports,tradepublication
Wheredoestheconversationtakeplace?
OneafternoonIwassittingatmyfavoritetableinarestaurant,waitingforthefoodIhadordered.SuddenlyI【36】thatamansit
PepysandhiswifeJanehadaskedsomefriendstodinneronSunday,September2nd,1666.TheywereupverylateontheSaturdaye
Wheredoesthisconversationtakeplace?
OnesillyquestionIsimplycan’tunderstandis"Howdoyoufeel?"Usuallythequestionisaskedofamaninaction—amanonthe
1.Needed:Full-timesecretarypositionopenApplicants(申请人)shouldhaveatleast2years’experience.ApplyinpersonatUn
Thousandsofyearsagomanusedhandyrocksforhissurgicaloperations.Laterheusedsharpbonesorhorns,metalknivesandmo
Thousandsofyearsagomanusedhandyrocksforhissurgicaloperations.Laterheusedsharpbonesorhorns,metalknivesandmo
随机试题
设f(x)具有二阶导数,试确定f(x),使曲线积分∫C[e-x-2f’(x)-f(x)]ydx+f’(x)dy与积分路径无关.
“阳脉之海”是指()
设备的()就是指设备从投人使用到因技术落后而被淘汰所延续的时间。【2005年考试真题】
()是期权的执行价格比现在的即期市场价格差。
人民检察院立案监督的内容是公安机关作出的()。
如图,某学校校园内有一块形状为直角梯形的空地ABCD,其中AB∥DC,∠B=90°,AB=100m,BC=80m,CD=40m,现计划在上面建设一个面积为S的矩形综合楼PMBN,其中点P在线段AD上,且PM的长至少为36m.边AD的长为
ODQDB同时支持(33)两种服务。DQDB子网的双总线结构由(34)总线以及接在这两条总线上的大量的节点组成。DQDB网络为双总线提供了(35)访问控制方式,其中能够提供非等时服务是(36),它用于(37)业务。
当派生类从一个基类保护继承时,基类中的一些成员在派生类中成为保护成员,这些成员在基类中原有的访问属性是()。
有以下程序段:k=5ForI=1t010step0k=k+2NextI执行该程序段后,结果是()。
Onceasourceof【B1】______businessactivity,Japan’skaraokeindustryhassloweddown.Japanesehavelesstosingaboutamid【B2
最新回复
(
0
)