六、当先行词被same修饰，且指“同一物品”时。如：
She is wearing the same dress that she wore yesterday.
七、关系代词在定语从句中作表语时。如：
a.This is no longer the place that it used to be. b.He is not the man that he was.
八、当主句是以who，which开头的特殊疑问句或先行词是who时。如：
a.Which is the book that he bought yesterday？ b.Who that you have ever seen can beat him in the game？
