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
2017-05-27
57
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://kaotiyun.com/show/8Grd777K
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
Itwasthedistrictsportsmeet.Myfootstillhadn’thealed(痊愈)froma(n)【36】injury.Ihad【37】whetherornotIshouldattendthe
WhatshouldthestudentsbringWiththemtotheexam?
ItwasClark’sfirstvisittoLondon:UndergroundRailway.Against【36】adviceofhisfriends,hedecidedtogothereafter5o’c
TodayIvisitedtheSmiths--myfirsttimevisit【76】______toaAmericanfamily.Theyliveinasmall
OneafternoonIwassittingatmyfavoritetableinarestaurant,waitingforthefoodIhadordered.SuddenlyI【36】thatamansit
OneafternoonIwassittingatmyfavoritetableinarestaurant,waitingforthefoodIhadordered.SuddenlyI【36】thatamansit
Thousandsofyearsagomanusedhandyrocksforhissurgicaloperations.Laterheusedsharpbonesorhorns,metalknivesandmo
Thousandsofyearsagomanusedhandyrocksforhissurgicaloperations.Laterheusedsharpbonesorhorns,metalknivesandmo
Thousandsofyearsagomanusedhandyrocksforhissurgicaloperations.Laterheusedsharpbonesorhorns,metalknivesandmo
随机试题
联合式构词法是由两个意义相同、相反或相对的词根联合起来构成新词的方法,在词内两个词根是平等的,没有主从、正副之分。根据上述定义,下列使用了联合式构词法的是:
躯体疾病起病缓,于早期和恢复期最常见的精神障碍是【】
简述法约尔组织管理理论的主要观点。
剑突下搏动常见于
系统性红斑狼疮的诊断标准中包括
人体自身合成油酸有关的酶是脂肪酸β氧化的限速酶是
A、硝酸甘油B、普萘洛尔C、维拉帕米D、硝苯地平E、双嘧达莫阻滞Ca2+内流、无抗心律失常作用()
进度计划的优化情况没有()。
关系模型的数据操纵即是建立在关系上的数据操纵,一般有【】、增加、删除和修改四种操作。
要求通过while循环不断读人字符,当读入字母N时结束循环。若变量已正确定义,以下正确的程序段是()。
最新回复
(
0
)