结构分析的基本原理：主谓层次、定语状语的表现形式。
先主谓 | 后定状 |
1. 一对主谓——SV 2. 多对主谓——并列句、并列谓语 3. 特殊主语——动名词、不定式、主语从句 4. 固定结构——There和It句型 5. *插入“废话”——I think、They say | 1. 介词词组——without learning 2. 分词词组——compared with others 3. 不定式词组——to inform us 4. 形容词词组 5. 从句（定语、状语） |
例题：3. Traditionally, __________in New England on Thanksgiving Day.
A. when served is sweet cider B. when sweet cider is served
C. is served sweet cider D. sweet cider is served
解析：这里缺少至少一对完整的“主+谓”，完全符合要求的是D。已给出的副词Traditionally,和介词词组in New England on Thanksgiving Day，都是做状语成分；选项A、B都是从句（本身只能是定状类），选项C语序错误。（句子大意：传统上，在新英格兰，感恩节上，sweet cider会被提供——目测sweet cider应属于饮食类。“甜苹果酒”）
由此可见：我们可用三分法来梳理复杂的句子——
例子1：
It can be helpful for people who have never quite been able to put a finger on why they feel the way they do, but randomly using these terms to describe yourself or others, with little understanding of what these conditions actually are or how people experience them, is problematic and it seems to be on the rise.
主谓 | 状 | 定 |
It can be helpful for people | who have never quite been able to put a finger on why they feel the way they do, | |
but randomly using these terms.........is problematic |
with little understanding of what these conditions actually are or how people experience them, | to describe yourself or others, |
and it seems to be on the rise. |
识别主句（并列的三个）：这对人们有帮助……但随意使用这些术语（来描述你自己或他人）是有问题的……这（现象）似乎在增加。
我们还可以继续针对从句进行解析，以获得更多精确信息——
主谓 | 状 | 定 |
who have never quite been able to put a finger on why they feel the way |
they do, | |
what these conditions actually are or how people experience them, | ||
那些从来无法搞清楚为什么他们为何有如此感觉（的人们）（注：词组put a finger on sth. = to discover the exact reason why a situation is the way it is）
这些状况实际上是什么、或人们如何经历（这些状况）
最后回看整个句子：
It can be helpful for people who have never quite been able to put a finger on why they feel the way they do, but randomly using these terms to describe yourself or others, with little understanding of what these conditions actually are or how people experience them, is problematic and it seems to be on the rise.
对于那些一直无法明确自己为何会有这种感觉的人来说，这些术语可能会有所帮助，但在不了解这些症状的实际含义、或人们如何体验这些症状的情况下，随意使用这些术语来描述自己或他人，则是有问题的，而且这种现象似乎正在增多。
