定语从句连接词 in which 的使用？急！请快回答·！！！！

It is the second time_____ you have made such a mistake.
这个从句缺少状语，不缺主语或宾语，所以用in which =when

只用which，不用that的情况：
引导非限制性定语从句时；
引导词前有介词时；
一个句子中若有两个定语从句，一个用that引导，另一个用which引导；
e.g. He bought a book that could give him much knowledge and which could help him to kill the time.

这是一个固定词组:make a mistake in ……（在某方面犯错误）

现在把介词“in”提前了，提到了空格处，再因为
介词后面表示物的+which
介词后面表示人的+whom
此处是表示物，所以用in which

当然，这句话，如果介词不提前的话，可以用“that”
It is the second time that you have made such a mistake in.

我认为用that
It is the second /first time that 为固定搭配