考研英语的语法速成：情态动词被动关系的主动表达法

　　1. want, require, worth(形容词)后面接doing也可以表示被动意义。

　　Your hair wants cutting

　　The book is worth reading

　　The floor requires washing.

　　2.need既可以用need to be done 也可以使用need doing ，两种形式都表达被动的意义

　　The house needs painting= the house needs to be painted.

　　The watch needed repairing= the watch needed to be repaired.