need等動詞后接不定式或動名詞均可，但語態不同

先看一題：

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

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

此題應選 A。表示“需要”的動詞 need，want，require等，其后可接動名詞(用主動式表示被動含義)或不定式(用被動式表示被動含義)：

這位老頭需要照顧。

a. The old man needs looking after.

b. The old man needs to be looked after.

你的頭發需要理了。

a. Your hair wants cutting.

b. Your hair wants to be cut.

這房子需要刷漆了。

a. The house requires painting.

b. The house requires to be painted.

但是在其他情況下，則用主動式或被動式不能隨便：

這部電影值得看兩遍。

正：The film is worth seeing twice.

誤：The film is worth to be seen twice.

誤：The film is worth being seen twice.

這本書很難理解。

正：The book is difficult to understand.

誤：The book is difficult to be understood.