be to doing sth的语法现象

be towards to doing sth 的用法 急求初中英语语法知识总结.　　例：need doing sth be supposed to do sth be used to doing sth? be due to doing sth. advice to be doing sth be due to doing sth? be equal to(doing)sth. 英语不错的来一下扒be devote to doing sth/devote oneself to doing sth/ Be used to do sth Be used to doing sth 后者的to为何做介词? 英语几个语法问题start to do sth 和start doing sth的区别stop doing sth ,s be refer doing sth to doing sth哪个是更合适的 be used to doing sth 的否定形式及举例