第3部分：概括大意與完成句子(第23～30題，每題1分，共8分)
閱讀下面這篇短文，短文后有2項測試任務：(1)第23～26題要求從所給的6個選項中為第2～5段每段選擇1個正確的小標題;(2)第27～30題要求從所給的6個選項中選擇4個正確選項，分別完成每個句子。請將答案涂在答題卡相應的位置上.
1. Children enjoy shouting at a high wall and hearing the sound come back to them. These sounds are called echoes (回聲). Echoes have given us a number of valuable tools.
2. Echo sounding devices were early used in making maps of the ocean floor. Sounds or ultrasonic (超聲的) sounds make good tools for determining how deep the water is under ships. Sometimes echoes from ultrasonic distance finding devices were prevented from working by fish swimming past or by the presence of large objects. So ultrasonic devices have been replaced by other tools.
3. Radar is now a familiar tool. Like many others it was an unexpected discovery. It was first observed by two researchers, who were studying sound communication. They were sending signals from a station on one side of a river in Washington,
D IC. to a vehicle across the river. They discovered that their signals were stopped by passing ships. They recognized the importance of this discovery at once.
4. All this was of course just a start, from which our present radar has developed. The word "radar," in fact, gets its name from the term "radio detection (檢測) and ranging." "Ranging" is the term for detection of the distance between an object and the radar set. Today, in our scientific age, it would be difficult to manage without radar.
5. One of the many uses of radar is as a speed control device on highways. When a person in an automobile is driving faster than the speed limit, radar will show this clearly and the traffic police can take measures to stop him.
6. A pilot cannot fly a plane by sight alone. Many conditions such as flying at night and landing in dense fog require the pilot to use radar. Human eyes are not very good at determining speeds of approaching objects, but radar can show the pilot how fast nearby planes are moving.
23 Paragraph 2__________.
24 Paragraph 3__________.
25 Paragraph 4__________.
26 Paragraph 5__________.
A Study of Sound
B Highway Police
C Working Principles
D Early Use of "Radar"
E Useful Tools
F Discovery by Chance
27 Echo-sounding devices were early used to__________.
28 Ultrasonic device were used to__________.
29 Police use radar on highways to__________.
30 Radar helps pilots to__________.
A detect nearby objects
B determine the depth of the ocean water
C decide how fast you drive
D stop passing ships
E map the ocean floor
F observe water flow
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