# 托福阅读“三步法” 搞定细节题

Q8 According to paragraph 2, what is the relationship between permeability and porosity?

A. The more pores a rock has, the higher its porosity but the lower its permeability

B. Rocks with many internal spaces that are not connected with each other will have high porosity but low permeability.

C. If water flows through a rock easily, it has permeability but low porosity.

D. Rocks that have high permeability have high porosity and vice versa.

Groundwater is stored in a variety of rock types. A groundwater reservoir from which water can be extracted is called an aquifer. We can effectively think of an aquifer as a deposit of water. Extraction of water depends on two properties of the aquifer: porosity, and permeability. Between sediment grains are spaces that can be filled with water. This pore space is known as porosity and is expressed as a percentage of the total rock volume. Porosity is important for water-storage capacity, but for water to flow through rocks, the pore spaces must be connected. The ability of water, or other fluids, to flow through the interconnected pore spaces in rocks is termed permeability. Fractures and joints have very high permeability. In the intergranular spaces of rocks, however, fluid must flow around and between grains in a tortuous path; this winding path causes a resistance to flow. The rate at which the flowing water overcomes this resistance is related to the permeability of rock.

A选项说，岩石的孔越多，多孔性就越高，渗透性越低。原文并没有说，多孔性越高，渗透性就越低。B选项说岩石的孔没有相连，那么就有高的多孔性和低的渗透性。这句话正好体现了原文的内容：多孔性是水的储存能力，小孔相连，水能留过，是渗透性。孔不相联系，那么水留过小孔的能力就自然很低。C是说如果水很容易的留过岩石的孔，就是有渗透性，但是多孔性很低。这个文章也没有说。D选项说岩石有高的渗透性就有高的多孔性，反之亦然。这个原文也没有说。

（1）找关键词。关键词包括名词，动词，形容词，比较级等等，不能仅仅局限于过去所学的大写，数字等等。

（2）找关键词所在句子。如果文章中没写出明确含有这个关键词的句子，那么我们需要读清楚文章的相关句，找到他们之间内在的逻辑联系。

（3）运用排除法。用排除法的时候一定要注意，要符合文章，文章中没有提到的一定是不能选的。

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