can't help do sth/can't help to do sth./can't help doing sth 有什么区别?

问题描述:

can't help do sth/can't help to do sth./can't help doing sth 有什么区别?
特别是前两个的区别,要详解,谢谢

正确来说,
can't help do something:不能帮忙做
can't help doing:忍不住...
以前一直以为can't help to do是正确句型,来到北美看了多少书写了多少文章才意识到can't help do才是对的.
不过如果要对国内的考试交待,还是国内怎么教的就怎么答吧.