有这样一道题，是考查except用法的：

A：Does he often come to see you?

B：No，the never comes ________ he is in trouble.

A. except B. except that C. except when D. except for

此题很容易误选B，因为后面是一个从句，所以很容易联想到except that，其实此题应选C。B，C 两者之后均接从句，其区别主要从句意上看：except when中的when有“当……时”之意，而except that则无此义。比较：

I know nothing about him except that he lives in Paris. 我除知道他住在巴黎外，其他情况一无所知。

I like her except when she’s angry. 除了她发怒的时候，我还是挺喜欢她的。

except作为介词，后接名词或代词(这是基本用法)，除了以上提到的后接that从句和when从句外，以下用法也需注意：

(1) 副词：She has never come late except recently. 除了最近一段时间，她从未迟到。

(2) 介词短语：The window is never opened except in summer. 除了在夏天外，这扇窗户从不打开。

(3) 不定式(注意是否带 to)：It had no effect except to make him angry. 除了惹他生气外，没产生任何效果。

There was little we could do except wait. 除了等待我们没有什么办法。

(4) what从句：I know nothing about it except what he told me. 除他告诉我的情况外，我对此事一无所知。

(5) where从句：My papers seem to be everywhere except where they ought to be. 我的文件似乎完全不在它们应该放置的地方。