开学课堂英语四级考试阅读练习（41）

　　In the past,telephone calls were made mostly over copper wires.Copper wires are heavy and bulky.Fiber optics are flexible,glass fibers.They are no thicker than a human hair.A wire cable is as thick as a mans arm.An optical fiber cable is as thick as a thumb.

　　Fiber optics transfer sound into light.First,a person speaks into a phone.The sound is changed into electrical impulses.A small laser changes the electrical impulses into coded bursts of light.The light is decoded hack into electrical impulses at the telephone recieving station.Finally,the electrical impulses are changed into sounds again at the receiving telephone.

　　Optical fibers transimit calls much faster than copper wires can.The laser pulses with light as fast as 90 million times a second.At that speed,every word in a dictionary can be sent through a single fiber in a few seconds.Optical fibers also save space.A few fibers can carry more calls than thousands of strands of copper cable.

　　Optical fibers will be used for video as well as voice communications.And they will prove useful in computer-to-computer hookups.However,it will take years to replace existing wires.

　　1.Which of the following best expresses the main point of the passage?

　　a.Fiber optics are flexible,glass fibers.

　　b.Copper wires have been used in most phone systems.

　　c.Fiber optics are an improvement in communication systems.

　　d.A few optical fibers can carry thousands of phone calls.

　　2.As it is used in the passage,the phrasefiber opticsmeans _____.

　　a.transmission of information by means of infra-red light signals aling a thin glass fiber.

　　b.material or substance formed from a mass of fibers.

　　c.a flexible fiber-optic instrument that is used to view objects

　　d.a composite material consisting of glass fibers in resin

　　3.Which of the following can not be inferred about fiber cables from the passage?

　　a.They carry light waves.

　　b.They can be used in many forms of communication.

　　c.They are better than copper wires.

　　d.They are shorter than copper wires.

　　4.You can infer from the passage that a cable is _____.

　　a.a group of wires or strands that are bundled together

　　b.a copper wire that is used to carry phone calls

　　c.a glass fiber that carrise coded bursts of light

　　d.a laser that changers electrical impulses into light

　　5.You can infer from the passage that the wordtransmit most nearly means _____.

　　a.carry from one place to another

　　b.pulse with light

　　c.operate quickly

　　d.speak

　　答案：cadaa