填空题

The modern age is an age of electricity. People are so used to electric lights, radios, televisions, and telephones that it is hard to (36) what life would be like without them. When there is a power failure, people (37) about in faint candlelight, cars (38) in the streets because there are no traffic lights to guide them, and food (39) . in silent in refrigerators. Yet people began to understand how electricity works only a little more than two centuries ago. Nature has (40) been experimenting in this field for millions of years. Scientists are discovering more and more that the living world may hold many interesting (41) of electricity that could benefit (42) All living (43) send out tiny pulses of electricity. (44) The brain, too, sends out brain waves of electricity, which can be recorded in an electric device. (45) —often so small that sensitive instruments are needed to record them. But for some animals, certain muscled cells have become so specialized as electrical generators that they do not work as muscle cells at all. (46)