[单项选择]

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 reduction 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 more cleanly than gasoline, in part because they have fewer, if any, carbon-carbon bonds and the hydro
A. responsibility
B. disadvantage
C. advantage
D. duty

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 reduction 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 more cleanly than gasoline, in part because they have fewer, if any, carbon-car-bon 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. It has a higher energy content than other alternative fuels.
D. Its use would reduce the vehicle emissions drastically.

In recent years, we have seen great progress in house building. The type of houses found in a certain part of the world depends to a certain extent on the building materials available there. Countries where stone is abundant tend to have more stone houses than a place where there is plenty of timber for example. However, climatic conditions affect the houses built to a greater extent.
In equatorial countries like Singapore and Malaysia, two main factors are responsible for the type of houses built: the heat of the sun and the fierceness of rainstorms. Our houses are light and airy but have steep roofs. In some places, houses are built on stilts because they may be in lowlying areas which get flooded easily.
In a hot and dry country such as Arabia, the houses are often box-shaped. They have thick stone walls which are painted white. White surfaces radiate heat while dark surfaces absorb it. The houses have
A. people there can move more easily
B. the houses won’t hurt people in an earthquake
C. less damage will be caused in an earthquake
D. people will not be affected by the earthquake