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In recent years scientists have found that the laser has a wide variety of applications, making it one of the most important inventions for improving our quality of life.
One important field in which the laser has many applications is communications. Scientists have found that the laser beam can transmit human voices; as a result, telephone companies are now using laser light signals to transmit telephone calls through extremely small cables that are capable of carrying many more transmissions than the standard telephone cables. An additional advantage is that these systems using the laser light signals are also able to transmit video telephone conversations.
Another, perhaps less-known, field in which lasers are helping improve the quality of life is metrology—the science of measurement. The extremely straight, narrow laser beam can be used to put the parts of a structure being built into the correct position to each other
A. standardize telephone cables
B. remove communications jams
C. improve the quality of human voices
D. increase the capacity of communications
Although recent years have seen substantial reductions in noxious pollutants from individual motor vehicles, the number of such vehicles has been steadily increasing. Consequently more than 100 cities in the United States still have levels of carbon monoxide, particulate matter, and ozone (generated by photochemical reactions with hydrocarbons from vehicle exhaust) that exceed legally established limits. There is a growing realization that the only effective way to achieve further reductions in vehicle emissions--short of a massive shift away from the private automobile—is to replace conventional diesel fuel and gasoline with cleaner-burning fuels such as compressed natural gas, liquefied petroleum gas, ethanol, or methanol.
All of these alternatives are carbon-based fuels whose molecules are smaller and simpler than those of gasoline. These molecules burn mom cleanly than gasoline, in part because they have fewer, if any, carbon-carbon bonds, and the hydrocarbons t
A. It is substantially less expensive than ethanol.
B. It could be provided to consumers through the existing motor fuel distribution system.
C. Its use would substantially reduce ozone levels.
D. Its use would make design improvements in individual vehicles feasible.
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