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
2019-08-27
33
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 perching 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.
How is the hawk’s eyesight better than ours?
选项
A、It can identify small items more quickly than we do.
B、It can see at a longer distance than we do.
C、It has more cones in the retina than we do.
D、It has bigger eyes than we do.
答案
B
解析
根据第一段中的“The hawk, for instance,has such sharp eyes that it can spot a dime on the sidewalk while perching 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)”可知,鹰的视力非常锐利,当它盘踞在帝国大厦的楼顶时,它能看清人行道上的一角硬币。据此可知,鹰眼可以从更远的距离看清物体,这是鹰眼强于人眼的地方,B项正确。
转载请注明原文地址:https://kaotiyun.com/show/C4UO777K
0
考博英语
相关试题推荐
Mostnewwordsaremadeupfromother,earlierwords;language-makingisaconservativeprocess,wastinglittle.Whennewwords
OurculturehascausedmostAmericanstoassumenotonlythatourlanguageisuniversalbutthatthegesturesweuseareunderst
TheEconomistIntelligenceUnit(EIU)earnestlyattemptstomeasurewhichcountrywillprovidethebestopportunitiesforahealth
MichaelYessis,anemeritusprofessorofSportsScienceatCaliforniaStateUniversity,maintainsthat"geneticsonlydetermines
ItisnotdifficulttobepessimisticaboutthefutureofEuropeanbusiness.【T1】ComparedwiththeawesomestrengthofAmericaa
It’sabouttimeparents______thegapsbetweenthemandtheirchildren.
Thecomingofautomationis______tohaveimportantsocialconsequences.
Wewerepleasedtonotethattheearlymorningdeliverydidn’t______tothetrafficjamofthebusycity.
Therewas______rainandsnowlastwinter.Sowehaveagoodharvestthissummer.
Achildwhohasoncebeenpleasedwithatalelikes,asarule,tohaveitretoldinidenticallythesamewords,butthisshould
随机试题
下列各项中,属于非标准审计报告的有()。
有一换热器,热流体为压力1.0MPa的饱和水蒸气,换热后冷凝为对应的饱和水。被加热介质为常压的工艺空气,进出口温度分别为100℃、160℃,流量为100kmol/h,换热器的热效率为95%。试求:此换热器的热损失?[已知空气的恒压热容为:cp*=30k
下列关于项目建设地区选择原则的说法中,正确的是()。
某工程在总包单位和一个不属于总包管理范围之内的专业分包单位之间进行工程交接时,《交接检查记录》中的见证单位应该为()。
大华有限公司为增值税一般纳税人,主要生产和销售甲产品,适用增值税税率17%,所得税税率25%。该公司2015年7月发生以下业务:(1)销售甲产品2000件,单位售价180元,增值税税率17%,收到支票已经送存银行。(2)支付上述销售业务的运杂费6000
下列选项中,应计入专利权入账价值的有()。
一般资料:求助者,男性,49岁,工人。案例介绍:求助者去年体检发现肺部阴影,经检查确诊为肺癌早期。经过半年多的治疗,病情基本稳定,各项指标也逐步恢复正常。但住院期间看到许多癌症转移复发的病友,很担忧自己的情况,于是密切观察自己的身体变化,身上长出
危害行为的基本形式有()。
1940年,毛泽东《新民主主义论》中指出,新民主主义革命的政治目标是
已知f(π)=2,且求f(0).
最新回复
(
0
)