填空题

The modern age is an age of electricity. People are so (47) to electric lights, radio, televisions, and telephones that it is hard to imagine what life would be like (48) them. When there is a power failure, people search (49) with the hands in darkness or candlelight, cars hesitate in the street (50) there are no traffic lights to guide them, and food (51) in silent refrigerators.
Yet people began to understand how electricity works only a little more than two centuries ago. Nature has (52) been experimenting in this field for millions of years. Scientists are (53) more and more that the living world may hold many interesting secrets of electricity that could benefit humanity.
All living cells send out (54) pulses of electricity. In fact, they are so small that sensitive (55) are needed to record them. As the heart beats, it sends out pulses of record; they form an electrocardiogram, which a doctor can study to determine how well the heart is working. It has been recently discovered that although individual cell only sends out small pulse, when large numbers of these cells are linked together, the effects can be (56) . Some interesting phenomenon in the animal world can thus be explained.

• A) aboutI) improve
• B) mapsJ) due to
• C) quickly K) used
• D) with L) tiny
• E) discovering M) apparently
• F) astonishing N) instruments
• G) spoils O) because
• H) without