长句拆解：先抓主干，再读修饰
把定语、原因和补充信息逐层放回去，读懂较长句子。
内容更新：
进入本课练习 →这一课学什么
- 先找主句的主语和谓语
- 看清连接词，再把背景和原因放回主干
先找主句的主语和谓语
The book that I bought yesterday is useful 的主干是 The book is useful；that I bought yesterday 说明是哪本书。句子里出现多个动词时，先辨认哪些属于从句，别直接把第一个动词当作主句谓语。
The message that Mei sent this morning was helpful.
小美今天上午发来的那条消息很有帮助。
The students who joined the club last week are preparing a show.
上周加入社团的学生们正在准备一个节目。
看清连接词，再把背景和原因放回主干
Although the bus was late, we arrived before the lesson started 的主句是 we arrived；although 部分是让步背景，before 部分交代时间。阅读时先确定发生了什么，再补充条件、原因和时间，不逐词按中文顺序硬拼。
Although it was raining, the students who lived nearby walked to school.
虽然在下雨，住在附近的学生们还是步行去学校了。
We changed the plan because the room that we had booked was unavailable.
我们改变了计划，因为预订的房间无法使用。