托福阅读细节题之4选2题型

首先，以TPO33-1 The First Civilization 中的第四题为例：

According to paragraph 2, what are TWO reasons why farmers chose river valleys for cultivation? To receive credit you must select TWO answers choices.

仔细读题后，不难发现该题问的是农民选择河谷作为耕种地的原因，所以需要关注表示因果关系的词。并且该题需要答题者提供2个原因，所以各位同学在定位信息后要关注表达并列和递进关系的词， 例如 also, in addition, as well as, besides等。解题时我们挑选farmers以及river valleys 组合定位，提高定位的准确性。

根据以上定位词，我们在第二段中定位到：“The real breakthrough took place when farmers began  to cultivate crops along the floodplains of river systems.” 该句定位信息陈述了这个重大的突破发生在农民开始在沿河的冲击平原种植粮食，但并未提供题目所需的原因解释。

因此，继续往下读信息“The advantage was that crops grown in such areas were not as dependent on rainfall and therefore produced a more reliable harvest. ”这个句子中的“in such areas”指的就是上文中提到的“floodplains of river systems”, 前后句呼应，证明继续往下读信息是正确的决定。

同时这句话中出现了表示因果关系的“therefore”,因此我们需要的原因1就呼之欲出了，即“The advantage was that crops grown in such areas were not as dependent on rainfall ”，也就是在该地区种植粮食的优势是不需要依赖雨水。

接着我们继续往下寻找原因2，接着原因1的句子往后读“An additional benefit was that the sediment carried by the river waters deposited nutrients in the soil, thus enabling the farmer to cultivate a single plot of ground for many years without moving to a new location.”

快速浏览该句，不难发现该句句首就已给出表示递进关系的信号词“additional”，并且也有表示因果关系的信号词“thus”，因此我们需要的原因2就是“the sediment carried by the river waters deposited nutrients in the soil”， 也就是由河水冲刷带来的沉积物将营养物质沉积在土壤里。此时我们再来浏览4个选项：

A. The soils in river valleys were rich in nutrients
　　B. The crops grown in river valleys were not completely dependent on rainwater
　　C. Farming techniques could not be easily applied to soils far from rivers
　　D. The heavier weight of river soil resulted in more reliable harvests.

对比我们之前读取出的亮点原因，不难发现答案就是A 、B选项。

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