初一英语下册哪些句型+动词-ing形式、动词不定式

。begin(start) doing/to do begin / start to do sth begin / start doing sth. 1) 谈及一项长期活动或开始一种习惯时，使用doing. How old were you when you first started playing the piano? 你几岁时开始弹钢琴？ 2) begin, start用进行时时，后面动词用不定式to do I w