5、For thousands of years, people thought of glass as something beautiful to look at. Only recently have they come to think of it as something to look through. Stores display their goods in large glass windows. Glass bottles that hold food and drink allow us to see the contents. Glass is used to make spectacles(銀鏡), microscopes, telescopes, and many other extremely useful and necessary objects.

      Until the Second World War, most of the glass used for optical instruments (光學(xué)儀器) was imported from Europe. However, during the war Americans could not get European glass, and they were forced to make their own. As a result, new kinds of glass were developed that had been unknown before. These new effects were achieved by mixing other chemical elements with the sand. Some of these new glasses are very strong and can resist many kinds of shocks. According to a legend, a very hard glass was invented by a Roman, who showed his discovery to the Emperor. When the Emperor saw the glass he feared that it would become more valuable than gold and silver, making his treasure worthless  Therefore, he had the glassmaker killed, and the secret was not discovered again for hundreds of years.

      In the 20th century, safety glass was invented for use in modern cars and planes. Safety glass is made by placing a layer of plastic between two layers of glass. When the outside layer of glass is broken, the pieces do not fly around and injure people. Some glass of this type is strong enough to resist bullets.

      Although in recent years plastics have replaced glass under conditions where glass might be easily broken, there are new uses being developed for glass that were never imagined in the past. Perhaps the greatest advantage of glass is that its constituent parts (組成) are inexpensive and can be found all over the world.

1. According to the passage, glass today is regarded as________.

     A. something beautiful to look at only

     B. something useful in many ways

    C, something useless except for displaying goods

    D. the only thing to make bottles with

2. Why did Americans begin to make their own glass during the Second World War?

    A. They could not obtain it from Europe.

    B. They refused to use European glass.

    C. The glass made in Europe was out of date.

    D. Their advanced techniques encouraged them to do so.

3. A legend says that when the Roman Emperor saw the hard glass ________.

    A. he accepted it with delight

    B. he gave the inventor a lot of gold

    C. he regarded it as worthless

    D. he disliked the discovery

4. All of the following concerning safety glass are discussed in the text EXCEPT ________.

    A. its uses           B. its strength           C. its structure         D. its limitations

5. According to Paragraph 4, which of the following is true of glass?

    A. Glass has been replaced by plastics.

    B. New uses of glass being developed will be very expensive.

    C. The constituent parts of glass are low in price.

    D. The constituent parts of glass cannot be found everywhere.