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. countering a flawed argument that dismisses a possible solution to problem
B. reconciling contradictory points of view about the nature of a problem
C. identifying the strengths of possible solutions to a problem
D. discussing a problem and arguing in favor of one solution to it
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. are light and airy
B. have steep roofs
C. are always built on stilts
D. are built to shelter from the harsh elements
W: Hi. John. I haven’t seen you for a few weeks.
M: Hi. Mary. I’ve been studying a lot for final exams.
W: Well, the term is almost over now.
M: Yeah. My brother is coming for a visit this summer, and we’d like to see some of the country. But traveling is so expensive.
W: Have you thought about camping
W: Camping I’ve never done that !
W: Oh. I think you’ll really like it. You can rent the equipment you need. It’s much cheaper than buying it or staying at a hotel.
M: What a good idea! We can drive until we find a nice spot and just camp wherever we like.
W: Well, not exactly. It’s usually illegal unless you camp in a designated area. But there are many national parks and camp grounds around the country.
M: But that takes all the fun out of it.
W: Not really. Besides, there are almost always conveniences like showers at camp grounds to make it a little easier.
A. He has been working.
B. He has been studying.
C. He has been on a camping trip.
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