关于having been done这个语法
是不是非谓语?
如果主句与从句主语相同,是不是省略从句主语 可以由have benn down变成having been done 或者独立主格也可以这么变?还有哪种情况可以用?
This done,we went home.=After this had been done,we went home
这句话 had been 怎么被省略了？