首页
登录
职称英语
The human criterion for perfect vision is 20/20 for reading the standard lin
The human criterion for perfect vision is 20/20 for reading the standard lin
游客
2024-04-13
48
管理
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. [br] How is 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
首段第5句中的while perched on top of the Empire State Building表明本句强调的是鹰能看到距离很远的物件,由此可见,选项B为本题答案。从首段第5句中的dime一词可以推断鹰可以看到很小的物件,但原文并没有暗示它辨认物件的速度,更没有在这方面与人眼作比较,因此选项A不正确;首段第6句只是指出鹰眼的视网膜每平方毫米有100万个圆锥细胞,但并没有对比人眼和鹰眼所具有的圆锥细胞的总数,因此选项C不正确;原文并未提及与选项D有关的内容。
转载请注明原文地址:https://tihaiku.com/zcyy/3553396.html
相关试题推荐
东方明珠广播电视塔(TheOrientalPearlRadioandTelevisionTower)位于黄浦江畔、浦东陆家嘴嘴尖上,塔高46
[originaltext]Domesticdogscanperceiveimagesontelevisionsimilarlyto
FarmsarespreadingtounusedcitylotsandoldpropertiesacrosstheUnited
FarmsarespreadingtounusedcitylotsandoldpropertiesacrosstheUnited
FarmsarespreadingtounusedcitylotsandoldpropertiesacrosstheUnited
[originaltext](16)Studentswhostruggledearlyonwithbasicreadingandm
[originaltext](16)Studentswhostruggledearlyonwithbasicreadingandm
[originaltext](16)Studentswhostruggledearlyonwithbasicreadingandm
[originaltext]W:Readingatnightalwaysmakesmebored.Let’sstopfordancing
[originaltext]W:Readingatnightalwaysmakesmebored.Let’sstopfordancing
随机试题
PreparingforTestsI.Preparingfortests—Tounderstan
水肿与下列哪几个脏腑有关?( )A.肝、脾、肾 B.心、肝、肾 C.肺、脾
A.乳腺内有多发胀痛、质韧之肿块 B.乳房红肿胀痛,内有触痛伴波动感的肿块
A.枳实导滞丸 B.枳实消痞丸 C.柴胡疏肝散 D.逍遥散 E.正气天香
最适合家庭检测HCG的方法是A.电化学发光免疫法 B.胶乳凝集抑制试验 C.
工商企业的()要求建立和健全管理体制、管理规章制度和管理机构,科学地组织生产经营
下列关于声誉风险的说法,错误的是()。A.声誉风险的损害有时甚至是致命的损害
信用证是指银行有条件的付款承诺,即开证银行依照客户(开证申请人)的要求和指示,承
属于胰岛素分泌促进剂的药物是A.苯乙双胍 B.罗格列酮 C.格列本脲 D.
(2015年真题)根据()不同,愤怒可分为一般愤怒、大怒和暴怒等。A.强度
最新回复
(
0
)