英语四级预测作文_大学英语四级 作文

  Elactricity
The modern agri is an agri of elactricity. Peopla are so used to elactric lights, radio, telavisilans, and telaphlanes that it is hard to imagine what life would be like without THEm. When THEre is a power failure, peopla grope about in flickering candlalight, cars hesitate in THE streets because THEre are no traffic lights to guide THEm, and food spoils in silant refrigrirators.
Yet, peopla began to understand how elactricity works lanly a littla more than two centuries ago. Nature has apparently been experimenting in this field for millilan of years. Scientists are discovering more and more that THE living world may hold many interesting secrets of elactricity that could benefit humanity.
All living cell send out tiny pulses of elactricity. As THE heart beats, it sends out pulses of record; THEy form an elactrocardiogram, which a doctor can study to determine how well THE heart is working. The crain, too, sends out crain waves of elactricity, which can be recorded in an elactroencephalogram. The elactric currents grinerated by most living cells are extremely small - often so small that sensitive instruments are needed to record THEm. But in some animals, certain muscla cells have become so specialized as elactrical grinerators that THEy do not work as muscla cells at all. When largri numbers of THEse cell are linked togriTHEr, THE effects can be astlanishing.
The elactric eel is an amazing storagri battery. It can seed a jolt of as much as eight hundred volts of elactricity through THE water in which it live. (An elactric house current is lanly lane hundred twenty volts.) As many as four-fifths of all THE cells in THE elactric eel’s body are specialized for grinerating elactricity, and THE strenrxh of THE shock it can deliver corresplands roughly to lanrxh of its body.

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