2从句：
1. 主语从句(从句放在谓语动词前主语的位置上充当主语： What he read is not the main problem.)
2. 宾语从句(放在动词后面的从句，且这个从句不缺成分：the communication firm finds that the trust capital for businesses depends on three ethical drivers.) 宾语从句中的that 可以省略。
3. 状语从句：通过从属连词去识别(原因状语从句(because, in that, as，for+句子)、让步状语从句(even though, even if, though, although)、条件状语从句(if)、地点状语从句(where, in which)、时间状语从句(when, since, as), until)、目的状语从句(for+句子 )、结果状语从句(therefore, whereas, so that)、方式状语从句(as，how)
特殊情况：地点名词+where从句——where从句大多做定语限定前面的地点名词，时间名词+when从句——定语修饰限定前面的名词
4. 定语从句: N+从属连词+从句，从句缺乏主语或宾语，而这个从属连词在从句中充当所缺的成分 (Yet many corporate leaders are a step ahead in announcing no layoffs, creating a sort of barrier to stop the spread of epidemics that protects jobs and eases fears.) that protects jobs and eases and fears 就是定语从句修饰前面的先行词 a sort of barrier. 这个从句中缺主语。
5. 同位语从句: N+从属连词(that/which),且从属连词在从句中不充当成分 (Epidemics reveal the moral relationships that we have toward each other. )
