"that"在定语从句中能做主语吗？谢哈

当然可以：
The man that is talking to the manager is his father.
跟经理讲话的那个男的是经理的爸爸。

可以阿

This is the book that(which) is newly published

可以啊
That is a good idea
那是个很不错的主意
That 主语
is 系动词
a good idea表语