I will never forget the terrible accident that happened last Monday.

问题描述:

I will never forget the terrible accident that happened last Monday.
这里的that作什么成分?

这里的 that 用作指示代词(复数形式是those),其指代意义同形容词用法,同时它还可以用作定语从句中的先行词;还可为了避免重复,代替前述名词.
that代指the terrible accident在从句中作主语吗?可以这么说,做happened的主语