托福阅读如何做修辞目的题呢？技巧三：巧用选项逻辑排除大法

　　选项中除了to后面的动词对做题很有用之外，其中的逻辑关系也值得我们好好分析，经常可以起到帮助我们缩小选择范围的作用。

　　例题三：

　　Scientists have known for some time that certain plants, called hyperaccumulators, can concentrate minerals at levels a hundredfold or greater than normal. A survey of known hyperaccumulators identified that 75 percent of them amassed nickel, cobalt, copper, zinc, manganese, lead, and cadmium are other minerals of choice. Hyperaccumulators run the entire range of the plant world. They may be herbs, shrubs, or trees. Many members of the mustard family, spurge family, legume family, and grass family are top hyperaccumulators. Many are found in tropical and subtropical areas of the world, where accumulation of high concentrations of metals may afford some protection against plant-eating insects and microbial pathogens.

　　8. Why does the author mention “herbs”, “shrubs”, and “trees”? （4）

　　○ To provide examples of plant types that cannot tolerate high levels of harmful minerals.

　　○ To show why so many plants are hyperaccumulators.

　　○ To help explain why hyperaccumulators can be found in so many different places.

　　○ To emphasize that hyperaccumulators occur in a wide range of plant types.

　　这道题中定位句和前一句的关联比较明显。定位句出现了代词they，指代的是前一句中的Hyperaccumulators，而定位句可以说在对Hyperaccumulators做一些列举来体现出它的范围广。

　　因此，我们可以判定这两句话之间就是指代关系或者后面通过列举说明前面的关系。而看回选项，b和c明显擅自添加了因果逻辑why，那我们就可以快速地排除掉这两个选项了。

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