need等动词后接不定式或动名词均可，但语态不同

先看一题：

The library needs __________，but it’ll have to wait until Sunday.

A. cleaning                        B. be cleaned                         C. clean                        D. being cleaned

此题应选 A。表示“需要”的动词 need，want，require等，其后可接动名词(用主动式表示被动含义)或不定式(用被动式表示被动含义)：

这位老头需要照顾。

a. The old man needs looking after.

b. The old man needs to be looked after.

你的头发需要理了。

a. Your hair wants cutting.

b. Your hair wants to be cut.

这房子需要刷漆了。

a. The house requires painting.

b. The house requires to be painted.

但是在其他情况下，则用主动式或被动式不能随便：

这部电影值得看两遍。

正：The film is worth seeing twice.

误：The film is worth to be seen twice.

误：The film is worth being seen twice.

这本书很难理解。

正：The book is difficult to understand.

误：The book is difficult to be understood.