怎么样理解由where and who 引导的从句?

怎么样理解由where and who 引导的从句?

where可引导多种从句,如定语从句、状语从句以及名词性从句.
〔误〕 Go to find your watch.It’s there where you left it.
〔正〕 Go to find your watch.It’s where you left it.
〔析〕where引导表语从句,相当于at the place where.
〔误〕 The place where there is water,there is life.
〔正〕 Where there is water,there is life.
〔析〕where引导地点状语从句,可以放在主句的前面,也可以放在主句的后面.
〔误〕 I can’t remember in which place I met him.
〔正〕 I can’t remember where I met him.
〔析〕where引导宾语从句,不能用in which.
who引导定语从句应注意的五个方面.
一、 who引导的定语从句的先行词是表示人的名词或代词.如：
The student who is answering the question is John.正在回答问题的那个学生是约翰.
Anybody who breaks the laws will be punished.任何违反法律的人都将受到惩罚.
二、 who是主格,在定语从句中作主语,此时不能省略.如：
The person who was here yesterday is a musician.昨天来这儿的那个人是位音乐家.
但在非正式英语中,who亦可作宾语,且可以省略.如：
The man（who）I saw just now is Mr Li.我刚才见到的那个人是李先生.
三、 在定语从句中,who在人称、数上和其前面的先行词保持一致.如：
Do you know the boy who is standing over there?你认识站在那边的那个男孩吗?
四、 若先行词中既有人又有物,关系代词用that而不用who.如：
He watched the children and boxes that filled the car.他看见了塞满汽车的孩子和箱子.
五、 若先行词前面有形容词最高级、序数词修饰,关系代词用that而不用who.如：
Yao Ming is the best basketball player that I know.姚明是我知道的最好的篮球运动员.
Tom is the first boy that left the room.汤姆是第一个离开这个房间的男孩.
who引导宾语从句,并充当从句的表语(有时作主语).如：
I don't know who I should invite to the party.我不知道该邀请谁参加聚会.
Go and see who is knocking at the door.去看看谁在敲门.