LED（Light Emitting Diode），中文名叫发光二极管，是一种固态的半导体器件，它可以直接把（）。

Computer Mouse

The basic computer mouse is an amazingly clever invention with a relatively simple design that allows us to point at things on the computer and it is very productive. Think of all the things you can do with a mouse like selecting text for copying and pasting, drawing, and even scrolling on the page with the newer mice with the wheel. Most of us use the computer mouse daily without stopping to think how it works until it gets dirty and we have to learn how to clean it. We learn to point at thing before we learn to speak, so the mouse is a very natural pointing device. Other computer pointing devices include light pens, graphics tablets and touch screen, but the mouse is still our workhorse.

The computer mouse was invented in 1964 by Douglas Englehart of Stanford University. As computer screens became popular and arrow keys were used to more around a body of text, it became clear that a pointing device that allowed easier motion through the text and even selection of text would be very useful. The introduction of the mouse, with the Apple Lisa computer in 1983, really started the computer public on the road to relying on the mouse for routine computer tasks.

How does the mouse work？ We have to start at the bottom, so think upside down for now. It all starts with mouse ball. As the mouse ball in the bottom of the mouse rolls over the mouse pad, it presses against and turns two shafts. The shafts are connected to wheels with several small holes in them. The wheels have a pair of small electronic light-emitting devices called light emitting diodes (LED) mounted on either side. One LED sends a light beam to the LED on the other side. As the wheels spin and a hole rotates by, the light beam gets through to the LED on the other side. But a moment later the light beam is blocked until the next hole is in place. The LED detects a changing pattern of light, converts the pattern into an electronic signal, and sends the signal to the computer through wires in a cable that goes out the mouse body. This cable is the tail that helps give the mouse its name. The computer interprets the signal to tell it where to position the cursor on the computer screen.

So far we have only discussed the basic computer mouse that most of you probably have or have used. One problem with this design is that the mouse gets dirty as the ball rolls over the surface and picks up the dirt. Eventually you have to clean your mouse. The newer optical mice avoid this problem by having no moving parts.

Most computer users want to know how the computer mouse works.

A．Right

B．Wrong

C．Not mentioned

A.单模光纤的纤芯大，多模光纤的纤芯小

B.单模光纤比多模光纤采用的波长长

C.单模光纤的传输频带窄，而多模光纤的传输频带宽

D.单模光纤的光源采用发光二极管（Light Emitting Diode），而多模光纤的光源采用激光二极管（Laser Diode）

● 光纤分为单模光纤与多模光纤，这两种光纤的区别是 （11） 。

（11）

A. 单模光纤的纤芯大，多模光纤的纤芯小

B. 单模光纤比多模光纤采用的波长长

C. 单模光纤的传输频带窄，而多模光纤的传输频带宽

D. 单模光纤的光源采用发光二极管（Light Emitting Diode），而多模光纤的光源采用激光二极管（Laser Diode）

听力原文： Astronomers have detected the most distant explosion ever witnessed in the heavens. It was a flash so powerful that they could observe the faint light as it came in from almost the edge of the known universe. The U. S. space agency's Swift satellite was routinely scouring the cosmos for exploding stars on September 4 when it spotted what scientists have since realized is the most distant such burst on record.

In astronomy, distance means time. The further something is away, the longer its light has been traveling to get to us. So the star blast is also the most ancient ever observed.

The exploding star the Swift satellite observed was typical of the death of a massive star. These blasts am the most powerful in the universe, sending out 100 million times the energy the Sun does in one year. They are not rare, but occur daily, emitting their light in high energy gamma rays. If you could see gamma rays, the sky would twinkle with such bursts.

According to the news, which of the following is NOT true？

A．The explosion detected is the most distant one ever witnessed.

B．The explosion detected is the most ancient one ever witnessed.

C．The explosion detected is typical of the birth of a massive star.

D．The explosion is the most powerful in the universe.

光纤分为单模光纤与多模光纤，这两种光纤的区别是(11)。

A．单模光纤的纤芯大，多模光纤的纤芯小

B．单模光纤比多模光纤采用的波长长

C．单模光纤的传输频带窄，而多模光纤的传输频带宽

D．单模光纤的光源采用发光二极管(Light Emitting Diode)，而多模光纤的光源采用激光二极管(Laser Diode)

The passage implies that ______.

A．LED bulbs are still expensive at present

B．the task of making LED the main source of artificial light is too difficult

C．LED traffic lights are used everywhere in the world

D．in order to fulfill the task of making LED the main light source, lightbulb makers have to work together with semiconductor manufacturers

What led the policemen to search for the flat？

A．The light

B．That piece of paper thrown away outside the flat.

C．The double lock.

D．The closed windows.

LED Lighting

1 An accidental discovery announced recently has taken LED lighting to a new level, suggesting it could soon offer a cheaper, longer-lasting alternative to the traditional light bulb. The breakthrough adds to a growing trend that is likely to eventually make Thomas Edison&39;s bright invention obsolete. LEDs are already used in traffic lights, flashlights, and architectural lighting. They are flexible and operate less expensively than traditional lighting.

2 Michael Bowers, a graduate student2 at Vanderbilt University, was just trying to make really small quantum dots, which are crystals generally only a few nanometers big. Quantum dots contain anywhere from 100 to 1,000 electrons. They&39;re easily excited bundles of energy, and the smaller they are, the more excited they get. Each dot in Bowers&39; particular batch was exceptionally small, containing only 33 or 34 pairs of atoms.

3 When you shine a light on quantum dots or apply electricity to them, they react by producing their own light, normally a bright, vibrant color. But when Bowers shined a laser on his batch of dots, something unexpected happened. He was surprised when a white glow covered the table. The quantum dots were supposed to emit blue light, but instead they were giving off a beautiful white glow.

4 Then Bowers and another student got the idea to stir the dots into polyurethane and coat a blue LED light bulb with the mix. The lumpy bulb wasn&39;t pretty, but it produced white light similar to a regular light bulb.

5 LEDs produce twice as much light as a regular 60 watt bulb and burn for over 50,000 hours. The Department of Energy estimates LED lighting could reduce U. S. energy consumption for lighting by 29 percent by 2025. LEDs don&39;t emit heat, so they&39;re also more energy efficient. And they&39;re much harder to break.

6 Quantum dot mixtures could be painted on just about anything and electrically excited to produce a rainbow of colors, including white. The main light source of the future will almost surely not be a bulb. It might be a table, a wall, or even a fork.

Paragraph 1 ______

A LED Lighting Is Not MatureB LED Lighting Will Replace Traditional LightingC Almost Everything Could Be the Main Light Source in the FutureD LED Lighting Has Many AdvantagesE Bowers Made an Unexpected DiscoveryF LED Light Bulbs Look Lumpy

Paragraph 3 ______

A LED Lighting Is Not MatureB LED Lighting Will Replace Traditional LightingC Almost Everything Could Be the Main Light Source in the FutureD LED Lighting Has Many AdvantagesE Bowers Made an Unexpected DiscoveryF LED Light Bulbs Look Lumpy

Paragraph 5 ______

A LED Lighting Is Not MatureB LED Lighting Will Replace Traditional LightingC Almost Everything Could Be the Main Light Source in the FutureD LED Lighting Has Many AdvantagesE Bowers Made an Unexpected DiscoveryF LED Light Bulbs Look Lumpy

Paragraph 6 ______

A LED Lighting Is Not MatureB LED Lighting Will Replace Traditional LightingC Almost Everything Could Be the Main Light Source in the FutureD LED Lighting Has Many AdvantagesE Bowers Made an Unexpected DiscoveryF LED Light Bulbs Look Lumpy

Unlike traditional lighting, LEDs do not give out heat so ______.

A traditional lighting is less durable and dearerB a laser excited the quantum dotsC America adopted LEDsD graduate students work hardE quantum dot mixtures are magicF it is more efficient

Edison&39;s bright invention is likely to be outdated because ______.

A traditional lighting is less durable and dearerB a laser excited the quantum dotsC America adopted LEDsD graduate students work hardE quantum dot mixtures are magicF it is more efficient

Something unexpected happened during Bower&39;s experiment when ______.

A traditional lighting is less durable and dearerB a laser excited the quantum dotsC America adopted LEDsD graduate students work hardE quantum dot mixtures are magicF it is more efficient

Over one quarter of energy consumption for lighting could be saved by 2025 if ______.

A traditional lighting is less durable and dearerB a laser excited the quantum dotsC America adopted LEDsD graduate students work hardE quantum dot mixtures are magicF it is more efficient

请帮忙给出每个问题的正确答案和分析，谢谢！