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The idea of a fish being able to generate electricity strong enough to light

游客2024-02-16  24
问题     The idea of a fish being able to generate electricity strong enough to light lamp bulbs--or even to run a small electric motor--is almost unbelievable, but several kinds of fish are able to do this. Even more strangely, this curious power has been acquired in different ways by fish belonging to very different families.
    Perhaps the best known are the electric rays, or torpedoes(电鳐), of which several kinds live in warm seas. They possess on each side of the head, behind the eyes, a large organ consisting of a number of hexagonal shaped cells rather like a honeycomb. The cells are filled with a jelly-like substance, and contain a series of flat electric plates. One side, the negative side, of each plate, is supplied with very fine nerves, connected with a main nerve coming from a special part of the brain. Current passes from the upper, positive side of the organ downwards, to the negative, lower side. Generally it is necessary to touch the fish in two places, completing the circuit, in order to receive a shock.
     The strength of this shock depends on the size of the fish, but newly born ones only about 5 centime-tres across can be made to light the bulb of a pocket flashlight for a few moments, while a fully grown torpedo  gives a shock capable of knocking a man down, and, if suitable wires are connected, will operate a small electric motor for several minutes.
    Another famous example is the electric eel. This fish gives an even more powerful shock. The system is different from that of the torpedo in that the electric plates run longitudinally(纵向) and are supplied with nerves from the spinal(脊骨) cord. Consequently, the current passes along the fish from head to tail. The electric organs of these fish are really altered muscles and like all muscles are apt (likely) to tire, so they are not able to produce electricity for very long.
    The power of producing electricity may serve these fish both for defence and attack. [br] The ideal title for this passage is______.
选项 A、The Eel
B、Torpedo
C、Electric Fish
D、Electric Power
答案 C
解析 文章的题目其实也就是对全文中心的归纳，整篇文章都在叙述有关能发电的特殊鱼类及其具体发电过程。A项“电鳗”当然不正确，全文说明的鱼类不只鳗鱼一类，且重点也不是鳗鱼而是其发电系统。B项电鳐也同样不正确，C项“发电的鱼”这显然与全文主题相切，D项“电力”这与全文巾题相切，D项“电力”这与全文中心差距太大，所以应选C项。
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