7. As a construction material, bamboo is as strong as steel and sturdier than concrete. Moreover, in tropical areas bamboo is a much less expensive construction material than either steel or concrete and is always readily available. In tropical areas, therefore, building with bamboo makes better economic sense than building with steel or concrete, except where land values are high.
Which of the following, if true, most helps to explain the exception noted above?

A、 Buildings constructed of bamboo are less likely to suffer earthquake damage than are steel and concrete buildings.
B、 Bamboo is unsuitable as a building material for multistory buildings.
C、 In order to protect it from being damaged by termites and beetles, bamboo must be soaked, at some expense, in a preservative.
D、 In some tropical areas, bamboo is used to make the scaffolding that is used during large construction projects.
E、 Bamboo growing in an area where land values are increasing is often cleared to make way for construction.

【正确答案】 B

【答案解析】 Argument Construction
Situation Bamboo is as strong as steel and sturdier than concrete when used as a construction material. In
tropical areas, bamboo is much less expensive and is always readily available.
Reasoning What explains the exception specified in the conclusion? The argument's conclusion is that in tropical
areas bamboo is a more economical building material than steel or concrete, except where land
values are high. The information in the passage makes clear why bamboo is a more economical
building material in tropical areas than are concrete or steel. So the question is: Why must an
exception be made for areas where land values are high? Multistory buildings are particularly
desirable in areas where land values are high, but bamboo may not be suitable for such buildings.
A This explains why bamboo would be preferable to steel or concrete in tropical areas especially prone to earthquakes. However, there is no clear connection to be made between areas where land values are high and areas especially prone to earthquakes.
B Correct. Multistory buildings provide a greater area of floor space for a given site area, and in that sense are more economical. A single-story building with the same floor space will occupy a much bigger site, so the higher the land values, the more likely it is that a multistory building will be built on that land. Thus, given this information, bamboo is less suitable for areas where land values are high.
C This undermines, to some extent, the claim that bamboo is an economical building material. But it does nothing to explain why it would be less economical specifically in areas where land values are high.
D This is irrelevant. Bamboo is used to build scaffolding for construction projects and as a building material for permanent structures. There is no way to infer from this that bamboo is less economical specifically in areas where land values are high.
E The fact that bamboo is cleared from an area to make room for construction in no way implies that bamboo would not be a suitable and economical building material for the area once it has been cleared.
The correct answer is B.