在这篇文章中：确定关系代词前所用介词的七点注意，例举了 in which case, at which point, at which time, by which time, during which time等等这几种常见搭配，无一例外的视为关系代词引导定语从句，故都没有使用其他连词，比如：

He may be busy, in which case I’ll call later. 

但我认为这里的which明显是指示限定词，本质上和this、that一样，而换成that句子肯定需要连词：

He may be busy, and in that case I’ll call later. 

那么这里的which到底是关系代词还是限定词呢？如果是限定词又为什么不需要连词呢？

期待诸位老师的解答，谢谢。