第3部分：概括大意與完成句子。下面的短文后有2項測試任務(wù)：(1)第23——26題要求從所給的6個選項中為第3——6段每段選擇1個最佳標題;(2)第27——30題要求從所給的6個選項中為每個句子確定1個最佳選項。

Maglev Trains

A few countries are using powerful electromagnets to develop high-speed trains, called maglev trains. Maglev is short for magnetic levitation1, which means that these trains float over a guide way using the basic principles of magnets to replace the old steel wheel and track trains.

If you’ve ever played with magnets, you know that opposite poles attract and like poles repel each other. This is the basic principle behind electromagnetic propulsion. Electromagnets are similar to other magnets in that they attract metal objects, but the magnetic pull is temporary. You can easily create a small electromagnet yourself by connecting the ends of a copper wire to the positive and negative ends of an AA-cell battery. This creates a small magnetic field. If you disconnect either end of the wire from the battery, the magnetic field is taken away.

The magnetic field created in this wire-and-battery experiment is the simple idea behind a maglev train rail system. There are three components to this system: A large electrical power source, metal coils lining a guide way or track, and large guidance magnets attached to the underside of the train.

The big difference between a maglev train and a conventional train is that maglev trains do not have an engine-at least not the kind of engine used to pull typical train cars along steel tracks4. The engine for maglev trains is rather innoticeable. Instead of using fossil fuels, the magnetic field created by the electrified coils in the guideway walls and the track combines to propel the trains.

The magnetized coil running along the track, called a guideway, repels the large magnets on the train’s undercarriage, allowing the train to levitate between 1 to 10 cm above the guideway. Once the train is levitated, power is supplied to the coils within the guideway walls to create a unique system of magnetic fields that pull and push the train along the guideway. The electric current supplied to the coils in the guideway walls is constantly alternating to change the polarity of the magnetized coils. This change in polarity causes the magnetic field in front of the train to pull the vehicle forward, while the magnetic field behind the train adds more forward thrust.

Maglev trains float on a cushion of air, eliminating friction. This lack of friction allows these trains to reach unprecedented ground transportation speeds of more than 500 kph, or twice as fast as the fastest conventional train. At 500 kph, you could travel from Paris to Rome in just over two hours.

23. Paragraph 3 _____

24. Paragraph 4 _____

25. Paragraph 5 _____

26. Paragraph 6 _____

A. The Main Components of the Maglev Train System

B. High-speed Maglev due to Zero Friction

C. The Working Principle of the Maglev Train

D. Differences between Polarity and Magnetic Field

E. Comparison of Maglev Trains with Traditional Ones

F. Maglev with a Powerful Motor

27. Several countries in the world are using strong electromagnets _____.

28. You can connect a wire to the positive and negative ends of a battery _____.

29. A unique system of magnetic fields is created by the coils _____.

30. The frictionless maglev train enables you _____.

A. to develop a maglev train rail system

B. to explain why maglev trains are faster

C. to pull and push the train forward

D. to create a magnetic field

E. to experiment with the maglev train

F. to travel from Paris to Rome in about two hours

參考答案：23-30 AEC BADCF

第4部分：閱讀理解。下面有3篇短文，每篇短文后有5道題。請根據(jù)短文內(nèi)容，為每題確定1個最佳選項。

Small But Wise

On December 14, NASA blasted a small but mighty telescope into space. The telescope is called WISE and is about as wide around as a trashcan. Don’t let its small size fool you: WISE has a powerful digital camera, and it will be taking pictures of some the wildest objects in the known universe,including asteroids, faint stars, blazing galaxies and giant clouds of dust where planets and stars are born.

“I’m very excited because we’re going to be seeing parts of the universe that we haven’t seen before,” said Ned Wright, a scientist who directs the WISE project.

Since arriving in space, the WISE telescope has been circling the Earth, held by gravity in a polar orbit (this means it crosses close to the north and south poles with each lap). Its camera is pointed outward, away from the Earth, and WISE will snap a picture of a different part of the sky every 11 minutes. After six months it will have taken pictures across the entire sky.

The pictures taken by WISE won’t be like everyday digital photographs, however. WISE stands for “Wide-field Infrared Survey Explorer.” As its name suggests, the WISE camera takes pictures of features that give off infrared radiation.

Radiation is energy that travels as a wave. Visible light, including the familiar spectrum of light that becomes visible in a rainbow,is an example of radiation. When an ordinary digital camera takes a picture of a tree, for example, it receives the waves of visible light that are reflected off the tree. When these waves enter the camera through the lens, they’re processed by the camera, which then puts the image together.

Waves of infrared radiation are longer than waves of visible light, so ordinary digital cameras don’t see them, and neither do the eyes of human beings. Although invisible to the eye, longer infrared radiation can be detected as warmth by the skin.

That’s a key idea to why WISE will be able to see things other telescopes can’t. Not everything in the universe shows up in visible light. Asteroids, for example, are giant rocks that float through space-but they absorb most of the light that reaches them. They don’t reflect light, so they’re difficult to see. But they do give off infrared radiation, so an infrared telescope like WISE will be able to produce images of them. During its mission WISE will take pictures of hundreds of thousands of asteroids.

Brown dwarfs are another kind of deep-space object that will show up in WISE’s pictures. These objects are “failed” stars-which means they are not massive enough to jump start the same kind of reactions that power stars such as the sun. Instead,brown dwarfs simply shrink and cool down. They’re so dim that they’re almost impossible to see with visible light, but in the infrared spectrum they glow.

31 .What is so special about WISE?

A. It is small in size but carries a large camera.

B. It is as small as a trashcan.

C. Its digital camera can help astronomers to see the unknown space.

D. Never before has a telescope carried a digital camera in space.

32. Which is NOT the synonym for the word "snap" in the third paragraph?

A. make.

B. shoot.

C. take

D. photograph.

33. The camera on WISE _____

A. is no different from an ordinary camera.

B. does not see infrared radiation while the ordinary camera does.

C. catches the infrared radiation while the ordinary camera does not.

D. reflects light that human eyes can see.

34. Which of the following is NOT correct about “asteroids” according to paragraph 7?

A. Asteroids float through space giving off visible light.

B. Asteroids do not reflect light that reaches them.

C. It is difficult to take asteroids’ pictures by ordinary cameras.

D. The WISE telescope can take pictures of asteroids

35.What is implied in the last paragraph?

A. Brown dwarfs give off visible light.

B. Brown dwarfs give off infrared radiation.

C. Brown dwarfs are power stars like the sun.

D. Brown dwarfs are impossible to see with the WISE telescope.

（責任編輯：中大編輯）

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