start to do sth与start doing sth与begin to do sth以及begin doing sth有什么区别?最后举例子.

start doing sth. 开始做某事（接着做前面那件事）...start to do sth.开始做某事（做另一件事）
begin doing sth （有意识）开始做某事...begin to do sth （无意识）开始做某事.