Perhapsthe fact many of these first studies considered only algae of a size that couldbe collected in a net, a practice that overlooked the smaller phytoplanktonthat we now know grazers are most likely to feed on, led to a de-emphasis ofthe role of grazers in subsequent research.

这个句子谓语动词的识别稍有难度。

1. the fact 后描述的部分是这个fact的具体内容，所以the fact后为同位语从句;托福和雅思哪个好

2. a practice ...to feed on 作同位语。only algae of a size后出现的that could be collected ina net 对前者解释说明作用，为典型的后者定语从句;

3. 类似的that overlooked the smallerphytoplankton that we now know grazers are most likely to feed on 修饰说明a practice, 即为后者的后者定语从句。其中 that we now know grazersare most likely to feed on 为the smaller phytoplankton 的后者定语从句。仔细分析，we now know 类似插入语，如果在之前加as则更像比较状语从句。当然这个定语从句也可以写成 on which we now knowgrazers are most likely to feed;

4. led to 为整句谓语动词，于是 a de-emphasis 为整句宾语。

整句主干很简单，即Perhaps the fact let to a de-emphasis.但主语后跟了自带一个小级别定语从句的后置定语从句，接着又跟了个自带一个后置定语从句(同样嵌套了自己的定语从句)的同位语，读句子过程中，我们的思路容易被这些非主干成分打断。

例句2

The hydrologic cycle, a major topic inthis science, is the complete cycle of phenomena through which water passes,beginning as atmospheric water vapor, passing into liquid and solid form asprecipitation, thence along and into the ground surface, and finally againreturning to the form of atmospheric water vapor by means of evaporation andtranspiration.

1. 大多数同学可以准确识别出全句的主系表结构;

2. a major topic 显然做前面hydrologic cycle 的同位语;

3. the complete cycle of phenomena 是一个标准的“A of B”结构，我们知道，of B修饰/限定/解释/说明 A，主词为A;

4. 看到through which…可知后面是个定语从句;which定语从句里主谓是water passes, 后面跟了beginning, passing和 returning 三组现在分词伴随状语。其中returning 部分稍稍复杂，bymeans of evaporation and transpiration 为这个伴随状语内部的方式状语;

5. 需要注意的是处于句首或句尾的伴随状语，必须和主语一致。本句中beginning, passing和 returning三个动作的发起者都是water. 如果不一致，则应转化为独立主格结构。

整句主干可简化为The circle is the circle, 只是表语后跟了较长的后置定语从句稍稍增加了难度。