For thousands of years, people thought of glass as something beautiful to look at. Only recently have they come to think of it a

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问题     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 and jars that hold food and drink allow us to see the contents. Glass is used to make eyeglasses, microscopes, telescopes, and many other extremely useful and necessary objects.
    Until the Second World War, most of the glass used for optical instruments 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 glasses were developed that had been previously unknown. 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. Legend has it that 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 present 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 plate glass. When the outside layer of glass is broken, the pieces do not scatter 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 the greatest advantage of glass is that its component parts are inexpensive and can be found all over the world.
New uses of glass are being developed on the ground that______.

选项 A、glass is not as safe as plastics
B、glass is not as strong and durable as plastics
C、glass is easily obtainable and inexpensive
D、glass is more and more widely used

答案C

解析 推理判断题。本题解题的关键在于注意最后一段中的“there are new uses being developed,for…”,这里表明了一对因果关系,for后面引出不断研发玻璃新用途的原因,由此可见,本题正确选项应为C。选项A和B中提到的玻璃的缺点虽在现实中也是有可能的,但文中并无字句说明因为这些缺点而要不断研发玻璃的新用途。
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