2019英语专四阅读练习100篇附答案:视力研究

2019英语专四阅读练习100篇附答案:视力研究

2019英语专四阅读练习100篇附答案汇总

　　The human criterion for perfect vision is 20/20 forreading the standard lines on a Snellen eye chartwithout a hitch. The score is determined by howwell you read lines of letters of different sizes from20 feetaway. But being able to read the bottom lineon the eye chart does not approximate perfectionas far as other species are concerned. Most birds would consider us very visuallyhandicapped. The hawk. for instance,has such sharp eyes that it can spot a dime on thesidewalk while perched on top of the Empire State Building+ It can make fine visualdistinctions 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 theeye, consisting mostly of cones. that provide visual distinctions. One fovea permits the bird, while in theair. 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, likebinoculars, on its prey at the same time. A frog's vision is distinguished by its ability toperceive things as a constant motion picture. Known as "bug detectors", a highly developedset of cells in a frog's eyes responds mainly to movingobjects. So, it is said that a frog sitting ina 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 dividewhat it sees into a pattern of dots. or mosaic. With this hind of vision, the bee sees the sunonly as a single dot, a constant point of reference. Thus. the eye is a superb navigationalinstrument that constantly measures the angle of its line of flight in relation to the sun. Abee's eye also gauges flight speed. And if that isnot 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 atother 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.

　　1. The Snellen eye chart measures one'seyesight by__________________.

　　A) the number of lines he reads

　　B) the distance he stands away from the chart

　　C) the speed at which he recognizes the letters

　　D) several integrative factors

　　2. How is hawk's eyesight better than ours?

　　A) It can identify small items more quickly than we do.

　　B) It can see ai a longer distance than we do.

　　C) It has more cones in che retina than we do.

　　D) It has bigger eyes than we do.

　　3. Monocular vision enables the kingfisher to__________________.

　　A) avoid farsightedness

　　B) be able to see underwater

　　C) move one eye at a time

　　D) focus its eyes on the prey

　　4. A bee finds its direction by_______________________.

　　A) dividing what it sees into thousands of dots

　　B) constantly gauging its flying speed

　　C) using the sun as a constant point of reference

　　D) measuring the angle of the sun

　　5. What is the main idea of the passage'?

　　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 me "perfect vision” of human eyes.

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