1. The hydrologic cycle,a major topic in this science,is the complete cycle of phenomena through which water passes,beginning as atmospheric water vapor,passing into liquid and solid form as precipitation,thence along and into the ground surface,and finally again returning to the form of atmospheric water vapor by means of evaporation and transpiration. (4)
水文循环(hydrologic cycle)，作为该学科中的一个主要课题，指的是水所经过的诸现象的整个循环过程，开始时是作为大气中的水蒸气，转而作为雨、雪、露、雹一类的降水量经过液体和固体形态，由此而沿着地层表面分布或进入地层表面，最终通过蒸发和散发作用再度回复到大气水蒸气的形态。
难句类型：复杂修饰、插入语、省略
水文循环(hydrologic cycle)，作为该学科中的一个主要课题，指的是水所经过的诸现象的整个循环过程，开始时是作为大气中的水蒸气，转而作为雨、雪、露、雹一类的降水量经过液体和固体形态，由此而沿着地层表面分布或进入地层表面，最终通过蒸发和散发作用再度回复到大气水蒸气的形态。
解释：beginning开始的一系列分词都是修饰主语The hydrologic cycle的，分别是beginning/passing/passing/returning.值得注意的是，thence along and into the grund surfacee 是thence passing along and entering into the ground surfacee的省略形式，但是看上去意思却很清楚。类似这样的省略，是出题者合理地利用了省略来达到改编学术论文时压缩文章篇幅的目的。
意群训练：The hydrologic cycle,a major topic in this science,is the complete cycle of phenomena through which water passes,beginning as atmospheric water vapor,passing into liquid and solid form as precipitation，thence along and into the ground surface,and finally again returning to the form of atmospheric water vapor by means of evaporation and transpiration.www.examw.com
2. Only when a system possesses natural or artificial boundaries that associate the water within it the hydrologic cycle may the entire system properly be termed hydrogeologic.(4)
只有当一个系统拥有自然的或人工形成的边界来把边界中的水与水文循环联系起来的时候，才有可能把整个的系统恰当的成为与水文地质学有关。
难句类型：复杂修饰、倒装
解释：only放在句首时，主句的情态动词may倒装，这是我们高中就已经学过的东西。然而句首的only与倒装的may距离如此之远，这在以前却没有见过，所以读上去让人不习惯。另外一个难点在于，前面的由when所引导的时间状语从句中，宾语boundaries后面跟了一个定语从句，that associate the water within it with the hydrologic cycle,而且从句中的associate with又被water within it所分开，读者还要分神去考虑it所指的是什么，所以读到后面倒装的may的时候，难免不知所云。
意群训练：Only when a system possesses natural or artificial boundaries that associate the water within it with the hydrologic cycle may the entire system properly be termed hydrogeologic.
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