4. 分隔式定语从句
　　定语从句一般紧跟在先行词之后，但有时会被其他句子成分与先行词隔开，从而构成分隔式定语从句。
　　The days are gone when power politics worked.
　　A new teacher will come tomorrow who will teach you French.

　　5.介词+关系代词(which/whom等)引出的定语从句
　　如果关系代词(which/whom等)在定语从句中作介词的宾语，那么这个介词可以提到从句前，构成“介词+关系代词(which/whom等)+定语从句”。在这种结构中关系代词不可以用that。
　　This is a subject about which we might argue for a long while.
　　The four travelers with whom I shared the room were pleasant people.