_______(在1世纪末就开始投入使用), this kind of energy had brought great convenience for human beings.
听力原文：Collecting waste, food or materials that can cause fires creates serious health risks. In the United States, it violates laws that were created to protect public safety and property.
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AN UNUSUAL SWIMMING CLUB
Members of a special club in Britain cheerfully leave the warmth CHEER
of their beds, while most sensible people are still fast 【C1】__ for SLEEP
an 【C2】__ swim in water with a temperature of only seven degrees ENERGY
centigrade. This may sound like 【C3】__ to you, but these swimmers MAD
firmly believe that it is 【C4】__ to do this, even in mid-winter. HEALTH
【C5】__ of the club requires daily swimming outdoors. However, MEMBER
for people net used to large 【C6】__ in temperature, DIFFERENT
it may net be such a good idea. While there is an 【C7】__ in IMPROVE
the blood circulation of people who swim 【C8】__ in icy water, REGULAR
it can be 【C9】__ to others. But when members are asked why they HARM
do it, the common 【C10】__ is that it makes them feel wonderful! RESPOND
【C1】__
Some businessmen have found it______by putting users into video -game -like virtual worlds.
How many books did Carson write before Silent Spring, and what were their titles？ ______.
Much family quarrelling ends when husbands and wives realize what these energy cycles mean and which cycle each member of the family has.