Questions 21-30
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. 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 – areas of the eye, consisting mostly of cones, that provide visual distinctions. One foveae 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.

21. What does the passage mainly discuss?
(a) limits of the human eye
(b) perfect vision
(c) different eyes for different uses
(d) eye variation among different species

22. The word “criterion” in line 1 is closest in meaning to
(a) standard
(b) need
(c) expectation
(d) rule

23. The phrase “without a hitch” in line 2 is closest in meaning to
(a) unaided
(b) without glasses
(c) with little hesitation
(d) easily

24. According to the passage, why might birds and animals consider humans very visually handicapped?
(a) humans can’t see very well in either air or water
(b) human eyes are not as well suited to our needs
(c) the main outstanding feature of human eyes is color vision
(d) human eyes can’t do what their eyes can do

25. The word “that” in line 10 refers to
(a) foveae
(b) areas of the eye
(c) cones
(d) visual distinctions

26. According to the passage, “bug detectors” are useful for
(a) navigation
(b) seeing moving objects
(c) avoiding bugs when getting food
(d) avoiding starvation

27. According to the passage, which of the following is NOT true
(a) kingfishers have monocular vision
(b) bees see patterns of dots
(c) hawks eyes consist mostly of cones that can allow it to scan with one eye at a time
(d) humans are farsighted in water

28. Where in the passage does the author discuss that eyes are useful for avoiding starvation?
(a) lines 5-9
(b) lines 10-14
(c) lines 15-19
(d) lines 20-25

29. The phrase “paling into insignificance” in line 23 is closest in meaning to
(a) fading away
(b) of less importance
(c) without colored light
(d) being reduced to little importance

30. Which of the following can be inferred from the passage?
(a) eyes have developed differently in each species
(b) bees have the most complex eye
(c) humans should not envy what they don’t need
(d) perfect vision is not perfect

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