9) 当先行词在主句中作表语，而关系代词在从句中作表语。

Shanghai is no longer the city that it used to be..

4. 由when / where / why引导的定语从句

① I know the reason why he came late.

我知道他为什么来晚了。

② This is the place where we lived for 5 years.

这就是我住过五年的地方。

③ I will never forget the day when I met Mr. Li.

我永远也忘不了遇到李先生的那天。

　先行词表示地点时，有时用where，有时用that（which）引导定语从句。这时要看从句的谓语动词是及物动词还是不及物动词。如果是及物动词就用that（which），否则用where。例如：

① This is the house where he lived last year.

这就是他去年住过的房子。

② This is the house that (which) he visited last year.

这就是他去年去过的房子。

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