第3部分：概括大意与完成句子(第23～30题，每题1分，共8分)
下面的短文后有2项测试任务：(1)第23～26题要求从所给的6个选项中为第1～4段每段选择1个最佳标题;(2)第27～30题要求从所给的6个选项中为每个句子确定1个最佳选项。
The Tiniest Electric Motor in the World
Scientists recently made public the tiniest electric motor ever built. You could stuff hundreds of them into the period at the end of this sentence. One day a similar engine might power a tiny mechanical doctor that would travel through your body to remove your disease.
The motor works by shuffling atoms between two molten metal droplets in a carbon nanotube. One droplet is even smaller than the other. When a small electric current is applied to the droplets, atoms slowly get out of the larger droplet and join the smaller one. The small droplet grows-but never gets as big as the other droplet-and eventually bumps into the large droplet. As they touch, the large droplet rapidly sops up the atoms it had previously lost. This quick shift in energy produces a power stroke.
The technique exploits the fact that surface tension-the tendency of atoms or molecules to resist separating-becomes more important at small scales. Surface tension is the same thing that allows some insects to walk on water.
Although the amount of energy produced is small-20 microwatts-it is quite impressive in relation to the tiny scale of the motor. The whole setup is less than 200 nanometers on a side, or hundreds of times smaller than the width of a human hair. If it could be scaled up to the size of an automobile engine, it would be too million times more powerful than a Toyota Camry’s 225 horsepower V6 engine.
In 1988, Professor Richard Muller and colleagues made the first operating micromotor, which was 100 microns across, or about the thickness of a human hair. In 2003, Zettl’s group created the first nanoscale motor. In 2006, they built a nanoconveyor, which moves tiny particles along like cars in a factory.
Nanotechnology engineers try to mimic nature, building things atom-by-atom. Among other things, nanomotors could be used in optical circuits to redirect light, a process called optical switching. Futurists envision a day when nanomachines, powered by nanomotors, travel inside your body to find disease and repair damaged cells.
23. Paragraph 2 _____
24. Paragraph 4 _____
25. Paragraph 5 _____
26. Paragraph 6 _____
A. An Introduction of a Toyota’s 225 Horsepower V6 Engine
B. A Description of the Nanomotor in Terms of Power and Size
C. Surface Tension
D. Previous Inventions of Nanoscale Products
E. The Working Principle of the Nanomotor
F. Possible Fields of Application in the Future
27. Doctors envision that the nanomotor would travel through human bodies to _____.
28. Surface tension means the tendency of atoms or molecules to_____.
29. Nanoconveyors could be used to_____.
30. Applying a small electric current causes atoms to _____.
A. remove disease
B. resist separating
C. shuffle between two molten metal droplets
D. power nanornachines
E. sop up molecules from the large droplet
F. transport nanoscale objects
第4部分：阅读理解(第31～45题，每题3分，共45分)
下面有3篇短文，每篇短文后有5道题。请根据短文内容，为每题确定1个最佳选项。
第一篇
Invisibility Ring
Scientists can’t yet make an invisibility cloak (斗篷) like the one that Harry Potter uses. But，for the first time，they’ve constructed a simple cloaking device that makes itself and something placed inside it invisible to microwaves.
When a person “sees” an object，his or her eye senses many different waves of visible light as they bounce off the object. The eye and brain then work together to organize these sensations and reconstruct the object’s original shape. So，to make an object invisible，scientists have to keep waves from bouncing off it. And they have to make sure the object casts no shadow. Otherwise，the absence of reflected light on one side would give the object away.
Invisibility isn’t possible yet with waves of light that the human eye can see. But it is now possible with microwaves. Like visible light，microwaves are a form of radiant energy. They are part of the electromagnetic spectrum (电磁波频谱), which also includes radio waves，infrared light，ultraviolet rays，X rays，and gamma rays. The wavelengths of microwaves are shorter than those of radio waves but longer than those of visible light.
The scientists’ new “invisibility device” is the size of a drink coaster and shaped like a ring. The ring is made of a special material with unusual ability. When microwaves (微波) strike the ring，very few bounce off it. Instead，they pass through the ring，which bends the waves all the way around until they reach the opposite side. The waves then return to their original paths.
To a detector set up to receive microwaves on the other side of the ring，it looks as if the waves never changed their paths as if there were no object in the way! So，the ring is effectively invisible.
When the researchers put a small copper loop inside the ring，it，too，is nearly invisible. However，the cloaking device and anything inside it do cast a pale shadow. And the device works only for microwaves，not for visible light or any kind of electromagnetic radiation. So, Harry Potter’s invisibility cloak doesn’t have any real competition yet.
31. Harry Potter is mentioned in the passage, because scientists
A. can now make an invisible cloak of the same kind as he uses.
B. try to make an invisible cloak of the same kind as he uses.
C. try to invent a device similar in idea to the invisible cloak he uses.
D. know that it is possible to make an invisible cloak of the same kind.
32. What is true of microwaves?
A. Their wavelengths are shorter than those of visible light.
B. Their wavelengths are longer than those of visible light.
C. They are different from visible light as they are a kind of radiant energy.
D. They are visible to the human eye.
33. What is NOT true of the invisibility device?
A. It is made of a special material with unusual ability.
B. Microwaves bounce off it when they strike it.
C. Microwaves pass through it when they strike it.
D. It bends the microwaves all the way around until they reach the opposite side.
34. What does the word “coaster” mean in the passage?
A. A disk or plate placed under a drinking glass to protect a table top.
B. A vessel engaged in coastal trade.
C. A roller coaster.
D. A resident of a coastal area.
35. Harry Potter’s invisibility cloak doesn’t have any real competition yet, because
A. scientists have not found out how his cloak works.
B. the cloaking device is a total failure.
C. the cloaking device works only for microwaves.
D. the cloaking device works only for visible light.
