26.The stages of sleep take on ____.
A) an irregular aspect. B) a regular aspect C) a punctual aspect D) a similar aspect
27.Stage 4 sleep lasts ____.
A) about 80 minutes
B) about 4060 minutes
C) about 30 munutes
D) about 2040 minutes
28.The brain waves are the slowest during ____.
A) stage 1 B) stage 2 and stage 3 C) stage 4 D) REM sleep
29.In the second paragraph the word “dart” means ____.
A) glare B) move rapidly or suddenly C) stop movingD) gaze
30.One of the features of REM sleep is that ____.
A) there are large slow waves, though rapid for the first few minutes
B) you have the deepest sleep
C) there are no brain waves
D) the brain waves are a little fast and the brain becomes a little active
Questions 31 to 35 are based on the following passage:
Designing a lens can be compared to playing chess. In chess a player tries to trap his opponent's king in a series of moves. In creating a lens a lens designer attempts to “trap” light by forcing all the rays arising from a single point in the subject to focus on a single point in the image, as a consequence of their passing through a series of transparent( 透明的) elements with precisely curved surfaces. Since in both cases the ultimate goal and the means by which it can be attained are known, one is tempted to think there will be a single best decision at any point along the way. The number of possible consequences flowing from any one decision is so large, however, as to bevirtually, if not actually, infinite. Therefore in lens design, as inchess, perfect solutions to a problem are beyond reach. Although this article will be concerned only with the design of photographic lenses, the same principles apply to all lenses.
The lens designer has one enormous advantage over the chess player: the designer is free to call on any available source of help to guide him through the staggering number of possibilities. Most of that help once came from mathematics and physics, but recently computer technology, information theory,chemistry, industrial engineering and psychophysics have all contributed to making the lens designer's job immeasurably more productive. Some of the lenses on the market today were inconceivable a decade ago. Others whose design is as much as a century old can now be massproduced at low cost. With the development of automatic production methods, lenses are made by the millions, both out of glass and out of plastics. Today's lenses are better than the best lenses used by the great photographers of the past.Moreover, their price may lower, in spite of the fact that 19thcentury craftsmen worked for only a few dollars a week and today's lenses are more complex. The lens designer cannot fail to be grateful for the science and technology that have made his work easier and his creations more widely available, but he is also humbled: it is no longer practical for a fine photographic lens to be designed from beginning to end by a single human mind.
31.Lens design and chess playing are similar in that ____.
A) the final goal and the means by which it can be reached are known
B) perfect solutions to a problem can be found
C) any one decision at any point along the way to the goal can bring numerous possible results
D) both A and C
32.The final goal of designing a lens is ____.
A) to trap the opponent's lenses
B) to focus light with lenses
C) to handmake lenses at low cost
D) to reflect light by means of curved surfaces
33.After the passage the author will talk about ____.
A) the principles of designing lenses
B) techniques of making contact lenses
C) the design of photographic lenses
D) styles of lenses
34.Which of the following words cannot be used to describe today's lenses?
A) More delicate. B) Cheaper. C) Numerous. D) Unpopular.
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