have to do ,Like to do.那为什么practice就不能加个do?同样都是动词啊。

这是动词惯用法：另外还有
finish doing sth.
enjoy doing sth.
keep doing sth.
can't stand doing sth.
mind doing sth.
介词+doing sth

不太清楚。。。。但老师说practice doing sth是个固定短语，have to do ,Like to do也都是固定短语吧