gre写作辅导：写作资料句子23
8. 科技和社会变化Inventions affect the size of populations, which in turn influences the course of history. Some inventions affect population directly: Improvements in sanitation, the development of cured for fatal illnesses, and more effective contraceptive techniques are examples. Some inventions can also have indirect effects on population: techniques that improve crop yields or permit long-term storage of food surpluses make it possible to support a larger population with a given amount of farmland. And improvements in military technology have had dramatic effects on the conduct of war and hence on population size.
9．对能量的要求
Throughout human history a central aspect of technological change has been the quest for new sources of energy to meet the needs of growing populations. That quest has given rise to a succession of energy technologies, each more sophisticated than the last.(animal power---steam-driven machines---internal-combustion engine---nuclear energy---fusion reaction, in which hydrogen atoms are fused into helium.)
Many people believe that societies can meet their growing energy needs by continually investing in more sophisticated technologies. This approach has led to the development of huge nuclear-power plants to replace oil-fueled generators, and it is widely hoped that investment in fusion, an even more complex technology, will eliminate the dangers posed by nuclear power.
The trend toward greater use of nuclear power to generate electricity has become a major social and political issue. Underlying the conflict over the safety of nuclear-power plants is the issue of control.
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