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
The human criterion for perfect vision is 20/20 for reading the standard lines on a Snellen eye chart without a hitch. The score
The human criterion for perfect vision is 20/20 for reading the standard lines on a Snellen eye chart without a hitch. The score
admin
2017-02-01
30
问题
The human criterion for perfect vision is 20/20 for reading the standard lines on a Snellen eye chart without a hitch. The score is determined by how well you read lines of letters of different sizes from 20 feet away. But being able to read the bottom line on the eye chart does not approximate perfection as far as other species are concerned. Most birds would consider us very visually handicapped. The hawk, for instance, has such sharp eyes that it can spot a dime on the sidewalk while perched on top of the Empire State Building. It can make fine visual distinctions because it is blessed with one million cones per square millimeter in its retina(视网膜). And in water, humans are farsighted, while the kingfisher, swooping down to spear fish, can see well in both the air and water because it is endowed with two foveae(凹窝)-areas of the eye, consisting mostly of cones, that provide visual distinctions. One fovea permits the bird, while in the air, to scan the water below with one eye at a time. This is called monocular vision. Once it hits the water, the other fovea joins in, allowing the kingfisher to focus both eyes, like binoculars, on its prey at the same time. A frog’s vision is distinguished by its ability to perceive things as a constant motion picture. Known as "bug detectors", a highly developed set of cells in a frog’s eyes responds mainly to moving objects. So, it is said that a frog sitting in a field of dead bugs wouldn’t see them as food and would starve.
The bee has a "compound" eye, which is used for navigation. It has 15,000 facets that divide what it sees into a pattern of dots, or mosaic. With this kind of vision, the bee sees the sun only as a single dot, a constant point of reference. Thus, the eye is a superb navigational instrument that constantly measures the angle of its line of flight in relation to the sun. A bee’s eye also gauges flight speed. And if that is not enough to leave our 20/20 "perfect vision" paling into insignificance, the bee is capable of seeing something we can’t—ultraviolet light. Thus, what humans consider to be "perfect vision" is in fact rather limited when we look at other species. However, there is still much to be said for the human eye. Of all the mammals, only humans and some primates can enjoy the pleasures of color vision.
What is the main idea of the passage?
选项
A、The differences between human eyes and other species’ eyes.
B、The advantages of other species’ eyes in comparison with human eyes.
C、The factors that make other species’ eyes better than human eyes.
D、The standard that determines the "perfect vision" of human eyes.
答案
A
解析
首段前3句通过描述人类测试视力的方法引出人类的视力不如其他物种这个话题,然后作者举了4个例子说明这个观点,而在第2段末句作者又指出人类视力在某一方面优于其他物种,由此可见,本文主要通过举例说明人类和其他物种在视力上的不同,由此可见,选项A概括了全文内容。第2段末句指出了人类视力也有优于其他物种视力的地方,选项B和C都强调其他物种的视力好,概括都不够全面;选项D只能概括文章首句的内容,其他的内容均未包括在内。
转载请注明原文地址:https://kaotiyun.com/show/WlF7777K
0
大学英语六级
相关试题推荐
A、Itreferstoabrand-newChristmaswithouttraditionalactivities.B、ItcelebratesChristmasonadifferentday.C、Itchanges
MoreandmorepeoplearetakingtheirtabletcomputerstobedtosurftheweborcheckFacebookore-mailsbefore【B1】_____thel
MoreandmorepeoplearetakingtheirtabletcomputerstobedtosurftheweborcheckFacebookore-mailsbefore【B1】_____thel
MoreandmorepeoplearetakingtheirtabletcomputerstobedtosurftheweborcheckFacebookore-mailsbefore【B1】_____thel
Amajoringredienttotakingthepainoutofastressfuldayatworkisasupportivepartnerathome,anewstudyhas【B1】_____.
A、Likeamanualworker.B、Likeanelegantprincess.C、Likearichwoman.D、Likeasuccessfulofficelady.C生活交际类,语义理解题。男士说派对女主人浑
A、Shewillhaveadiscussionwiththosewhowanttobevolunteers.B、Shewillworkwithtrainingagenciestoimproveteachingsk
Fertilizerusehasexploded,overloadingplantsworldwide,likelyalteringecosystemsfordecadestocenturies,scientistsrepor
DoBritain’sEnergyFirmsServethePublicInterest?[A]Capitalismisthebestandworstofsystems.Lefttoitself,itwillemb
FrustratedwithdelaysinSacramento,BayAreaofficialssaidThursdaytheyplannedtotakemattersintotheirownhandstoregu
随机试题
封闭后出现咬合过高时需调合的封闭剂是
多个警示牌一起布置时,其从左到右的排序应为()。
移动通信网络测试中的拨打测试选点原则有()。
机电工程注册建造师执业的冶炼工程包括()等工程。
当事人申请仲裁的,经仲裁委员会认为符合受理条件的,告知当事人的时间应在收到仲裁申请书的()日之内。
影响供给价格弹性的是()。
甲公司有关投资业务资料如下(不考虑所得税影响,甲公司按照净利润的10%提取盈余公积):资料一:2×17年7月1日,甲公司以银行存款7500万元从其他股东处购买了乙公司5%的股权。甲公司与乙公司的原股东在交易前不存在任何关联方关系,假定甲公司对乙公司5%
在损失补偿原则基础上又派生出的保险原则是()
外存上存放的数据()。
A、Hemisseshisflight.B、Hecanfindagoodseat.C、Hecanleavetheairportfirst.D、Hisluggagecomesoutlast.C短文说,你知道谁在下飞机
最新回复
(
0
)