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
2019-06-23
66
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/3VX7777K
0
大学英语六级
相关试题推荐
Comparisonsweredrawnbetweenthedevelopmentoftelevisioninthe20thcenturyandthediffusionofprintinginthe15thand1
Comparisonsweredrawnbetweenthedevelopmentoftelevisioninthe20thcenturyandthediffusionofprintinginthe15thand1
A、Theydon’tneedconventionalsignsandsymbols.B、Theyonlyrequireareceiverincommunication.C、Thedistancebetweencommun
Theincreaseinglobaltrademeansthatinternationalcompaniescannotaffordtomakecostlyadvertisingmistakesiftheywantt
A、Becausehumanbeingsarepowerfulenoughtokilloneanother.B、Becauseeveryspecieswillbecomeextinctbynaturalselection
Shoppinghasbecomeaverysecretandmysteriousaffair.Conspicuousconsumptiondoesnotlookgoodduringarecession,whichex
A、Tuesdaymorning.B、Tuesdayafternoon.C、Thursdaymorning.D、Thursdayafternoon.B男士说,葬礼在星期二举行,遗体吊唁仪式安排在下午。所以答案是B。对话提到两个时间点,星期二
A、Thefrequenttraindelays.B、Thefoodsoldonthetrains.C、ThemonopolyofBritishRailways.D、Thehightrainticketfares.C
FrustratedwithdelaysinSacramento,BayAreaofficialssaidThursdaytheyplannedtotakemattersintotheirownhandstoregu
Smokersinthe"landofthefree"arefindingthemselvesincreasinglylessfreetopursuetheirhabit.NewYorkCityofficialsa
随机试题
治疗牛急性瘤胃臌气时,瘤胃穿刺放气的正确做法是于
被保险人之间体现的是互相竞争的关系,表现在一定时期内少数被保险人遭受的损失实际上全部由保险人来分担。()
张明达以50万元购买一房屋出租,假设15年后该房将按价格40万元出售,如果要实现每年8%的投资报酬率,那么,该期间每年至少应有( )万元净租金收入。(取最接近金额)
采购物品定价法中属于自我定价的是()。
注意的基本特征是()。
Modernliberalopinionissensitivetoproblemsofrestrictionoffreedomandabuseofpower.(1)_____,manyholdthatamancan
What’stheaverageincreaseperyearofforeignstudentpopulationintheperiodbetween1985and1990intermsofpercentage?
A、Sheisreading.B、Sheistall.C、SheisacashieratMoonHotel.D、Sheisill.C题目问的是“你妈妈是干什么的?”这是一个询问职业的表达,只有C项“她是月亮宾馆的收银员”符合
TheEnvironmentalProtectionAgencyunveiledadetailedproposalWednesdayforusingthegovernment’sregulatorypowerstocurb
FromGolda:theLifeofIsrael’sPrimeMinisterTheStrugglewithHerParentsoverHerEducationWhenGoldagraduatedas
最新回复
(
0
)