(1)并列、递进关系：and，or，besides，furthermore，what’s more，then，in addition，moreover，in other words;
(2)因果关系：as a result of，on account of ，as a result ，thanks to，therefore，hence，consequently，because，for，due to，owing to;
文章首段首句往往会告知文章的背景或是主题，掌握首段首句可以帮助我们确定文章接下来要谈论的内容，做到心中有数，不至于理解错误。如开篇Millions of Americans are entering their 60s and are more concerned than ever about retirement. 这句话就告知我们这篇文章是谈论美国老龄人的退休问题。如果大家通过首段首句不能确定文章主题，可以看一下首段全部内容或是各个自然段的首尾句。
2.、词性分配的基本比例: 3~4个名词正确答案 + 1~2个名词干扰答案;3~4个动词正确答案+ 1~2个动词干扰答案;2~3个形容词正确答案 + 1个形容词干扰答案; 2~3个副词正确答案 + 1个副词干扰答案。
These optical illusions occur because the brain is constantly matching its model of reality to signals from the body’s sensors and interpreting what must be happening—that your brain must have moved, not the other; that downward motions is now normal, so a change from it must now be perceived as upward motion.
The sensors that make this magic are of two kinds. Each eye contains about 120 million rods, which provide somewhat blurry black and white vision. These are the windows of night vision; once adapted to the dark, they can detect a candle burning ten miles away.
Color vision in each eye comes from six to seven million structures called cones. Under ideal conditions, every cone can “see” the entire rainbow spectrum of visible colors, but one type of cone is most sensitive to red, another to green, a third to blue.
Rods and cones send their messages pulsing an average 20 to 25 times per second along the optic nerve. We see an image for a fraction of a second longer than it actually appears. In movies, reels of still photographs are projected onto screens at 24 frames per second, tricking our eyes into seeing a continuous moving picture.
Like apparent motion, color vision is also subject to unusual effects. When day gives way to night, twilight brings what the poet T.S. Eliot called “the violet hour.” A light levels fall, the rods become progressively less responsive. Rods are most sensitive to the shorter wavelengths of blue and green, and they impart a strange vividness to the garden’s blue flowers.
However, look at a white shirt during the reddish light of sunset, and you’ll still see it in its “true” color—white, not red. Our eyes are constantly comparing an object against its surroundings. They therefore observe the effect of a shift in the color of illuminating on both, and adjust accordingly.
The eyes can distinguish several million graduations of light and shade of color. Each waking second they flash tens of millions of pieces of information to the brain, which weaves them incessantly into a picture of the world around us.
Yet all this is done at the back of each eye by a fabric of sensors, called the retina, about as wide and as thick as a postage stamp. As the Renaissance inventor and artist Leonardo da Vinci wrote in wonder, “Who would believe that so small a space could contain the images of all the universe?”
1. Visual illusions often take place when the image of reality is ___.
A. matched to six to seven million structures called cones.
B. confused in the body’s sensors of both rods and cones.
C. interpreted in the brain as what must be the case.
D. signaled by about 120 million rods in the eye.
2. The visual sensor that is capable of distinguishing shades of color is called ___.
B. color vision
3. The retina send pulses to the brain ___.
A. in short wavelengths
B. as color pictures
C. by a ganglion cell
D. along the optic nerve.
4. Twenty-four still photographs are made into a continuous moving picture just because ___.
A. the image we see usually stays longer than it actually appears.
B. we see an object in comparison with its surroundings.
C. the eyes catch million pieces of information continuously.
D. rods and cones send messages 20 to 25 times a second.
5. The author’s purpose in writing the passage lies in ___.
A. showing that we sometimes are deceived by our own eyes.
B. informing us about the different functions of the eye organs.
C. regretting that we are too slow in the study of eyes.
D. marveling at the great work done by the retina.