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
2016-07-17
78
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/Ziud777K
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
Whatdoestheword"prestigious"inthesecondparagraphprobablymean?ManyAmericansareinterestedinChinabecause______.
Usually,______careforchildren’s______.
假定你叫李华,是中州市第27中学的学生。你前不久在《中国日报》上读到一篇有关农村(countryside)儿童辍学(leavesschoolatanearlyage)的报道。你于2009年1月14日给编辑写去一封信,谈了农村儿童辍学的主要原因以及
Theunderlinedword"guaranteed"inthepassageprobablymeans"______".IftheIrishexpecttoenjoythe5%ofreductionatpr
Languagelearningbeginswithlistening.Individualchildrenvarygreatlyintheamountoflisteningtheydobeforetheystarts
Whatwillthetwospeakersdothisweekend?
Wheredoestheconversationprobablytakeplace?
Formanypeopletoday,readingisnolongerrelaxation.Tokeepuptheirworktheymustreadletters,reports,tradepublication
Cars!!!Holidays!Thousandsofprizes!Hurry!FREEwitheverypacketofSPLASH!Yourpersonalluckynumber!Willbeamon
Whenistheirflight?
随机试题
2014年4月1日,甲融资租赁公司与乙公司订立一份融资租赁合同。该合同约定:甲公司(出租人)按照乙公司(承租人)的选择,从丙公司(出卖人)购进一套医疗设备租赁给乙公司使用;租赁期限为10年,从设备交付时起算;年租金400万元(每季度支付100万元),从设备
现行的《献血和输血的伦理规范》通过于
维生素D的生理活性形式是
可用于治疗风湿痹痛的药物有
下列财产应该收归国家所有的是()。
一项工程由甲,乙,丙三个工程队共同完成需要15天,甲队与乙队的工作效率相同,丙队3天的工作量与乙队4天的工作量相当。三队同时开工2天后,丙队被调往另一工地,甲乙两队留下继续工作,那么开井22天后,这项工程:()
请观察
为了使世袭王权为众多诸侯所确认,夏启在都城阳翟召集众多诸侯,举行盛大的(),夏王朝的统治基础得以完全确立了。
表达式a+=a-a=9的值是()。
Almosteverynewinnovationgoes【C1】______threephases.【C2】______initially【C3】______intothemarket,theprocessof【C4】______is
最新回复
(
0
)