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  3. The making of glass is a very old industry--at least 4,500 years old. Glass has many extraordinary qualities and it is frequentl

The making of glass is a very old industry--at least 4,500 years old. Glass has many extraordinary qualities and it is frequentl

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问题     The making of glass is a very old industry--at least 4,500 years old. Glass has many extraordinary qualities and it is frequently being used in new ways.
    One of the most interesting new uses for glass is in telephone communication. Scientists have developed glass fibers as thin as human hair, which are designed to can-y light signals. When the light reaches the other end, it is first changed into electrical signals, which are in turn converted into sound messages.
    Called light wave communication, the new system was used successfully in an experiment in Chicago in 1997. During the experiment, two glass fibers were able to carry 672 conversations at the same time. The lightwave cable, containing 144 glass fibers, has the capacity to carry 50,000 conversations at the same time.
    The lightwave communication system has two important advantages. First, the glass fiber cables are smaller and weigh less than copper. Second, they cost less.
    Perhaps it can be said that telephone communication has entered the age of light.
Which of the following statements best expresses the main idea of the passage?
选项 A、Glass is very useful because it has many unusual qualities.
B、Light signals have changed the use of glass in industry.
C、Glass fibers have reduced the cost of telephone communication.
D、The use of glass fibers to carry telephone messages is an interesting new development.
答案D
解析 第二段第一句和第二句讲的是玻璃纤维在通讯领域的新发展，应该是本篇文章的中心思想，可以判断D正确。
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