need/want/require/worth
注意：當 need, want, require, worth(形容詞)後面接doing也可以表示被動。
Your hair wants cutting.你的頭髮該理了。
The floor requires washing. 地板需要衝洗。
The book is worth reading.這本書值得一讀。
典型例題
The library needs___, but it'll have to wait until Sunday.
A. cleaning B. be cleaned C. clean D. being cleaned
答案A. need (實意) +n /to do，need (情態)+ do，當爲被動語態時，還可need + doing. 本題考最後一種用法，選A。如有to be clean 則也爲正確答案。
典：done，"不可能已經"。must not do 不可以（用於一般現在時)。