egin（start） doing/to do begin / start to do sth /begin / start doing sth. a） 谈及一项长期活动或开始一种习惯时,使用doing.例如： How old were you when you first started playing the piano? 你几岁时开始弹钢琴? b） begin, start用进行时时,后面动词用不定式to do.例如： I was beginning to get angry.我开始生起气来.
