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.例如:
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.例如:
I was beginning to get angry.我开始生起气来。
3) 在attempt, intend, begin, start 后接know, understand, realize这类动词时,常用不定式to do.例如:
I begin to understand the truth.我开始明白真相。
4) 事物作主语时。例如:
The snow began to melt.雪开始融化了