Not all sounds made by animals serve as language, and we have only to turn to that extraordinary discovery of echolocation (回声定位) in bats to see a case in which the voice plays a strictly practical role.

　　To get a full appreciation of what this means we must turn first to some recent human inventions. Everyoneknows that if he shouts near a wall or a mountainside, an echo will come back. The further off this solid obstacle, the longer time it will take for the return of the echo. A sound made by tapping on the main body of a ship will be reflected from the sea bottom, and by measuring the time interval between the taps andthe receipt of the echoes the depth of the sea at that point can be calculated. So was born the echo-sounding equipment, now in general use in ships. Every solid object will reflect a sound, varying according to the size and nature of the object. A shoal of fish will do this. So it is a comparatively simple step fromlocating the sea bottom to locating a shoal of fish. With experience, and with improved equipment, it is now possible not only to locate fish but to tell if it is herring, cod, or other well-known fish, by the pattern of its echo.

　　A few years ago it was found that certain bats emit squeaks (吱吱声) and by receiving 'he echoes they could locate and steer clear of obstacles--or locate flying insects on which they feed. This echolocation in bats is often compared with radar, the principle of which is similar.

　　练习题：

　　Choose correct answers to the question:

　　1.The main purpose of this passage is to ______.

　　A. describe that animals can make different sounds

　　B. prove that animals' voices can play practical roles

　　C. inspire the readers to make more inventions

　　D. startle the readers with some shocking facts

　　2. The discovery of echolocation may help with all of the following EXCEPT

　　A. measuring the depth of the sea

　　B. distinguishing different kinds of fish

　　C. improving the functions of radar

　　D. varying the size and nature of an object

　　3. By saying "A shoal of fish will do this"(Lines 6-7, Para. 2), the author means ________.

　　A. only one special kind of fish can reflect sounds

　　B. only one special kind of fish can be used to help locate a ship

　　C. a large group of fish can reflect sounds

　　D. a large group of fish can be used to help locate a ship

　　4. As it is discussed in the passage, the squeaks of bats can be functionally compared with ________.

　　A. human languages

　　B. a mountainside

　　C. a shoal of fish

　　D. taps on a ship

　　5. Which of the following statements can be inferred from the passage?

　　A. Animals are more intelligent than humans.

　　B. Humans are more intelligent than animals.

　　C. Animals are often compared with human inventions.

　　D. Humans are often inspired by animals.

　　1.[B] 主旨大意题。文章第1段就点明主题，明确指出以蝙蝠为例，动物发出的声音有实际作用，只有B可以概括文章的这个写作目的。

　　2.[C] 事实细节题。本题考査列举处，可用排除法解答。A、B、C在文中都有相关提及。D利用第2段中的varying制造干扰。在原文中，指的是回声因障碍物的不同而不同，而D偷换概念、曲解文意，D中的varying为及物动词，意为“改变”,显然不可能是回声定位的发现带来的功效。

　　3.[C] 词义推断题。本题考查对shoal的词义推测及代词this的理解。依据第2段最后几句话,可推测出a shoal of fish指的是“海里的一群鱼”;this则是指上一句提到的“任何固体都可以反射声音”，因此这句话表明一大群鱼就能像一个固体一样反射声音。

　　4.[D] 推理判断题。根据最后一段可知，蝙蝠发出吱吱声可以探测障碍物的距离，而第2段也指出轻敲船体可测知海底的距离，因此在功能上,D与蝙蝠的吱吱声相同。A中的human languages在文中未提到;B和C在文中各自的例子中充当的都是障碍物的角色，因此都不正确。

　　5.[D] 推理判断题。文章先说动物的回声定位功能,再说到回声定位探测仪的发明,由此可见，是动物的某些能力启发了人类的创造，因此只有D可从文中推测。文章并没有从智力方面比较人类和动物，因此可以排除A 和B;尽管文章说到了蝙蝠和雷达的原理相似，但是C中的often一词无据可循，且C的说法浮于表面，没有说到重点，故排除。