I am happy to do sth.I am happy doing sth.这里to do sth、doing

I meant to do sth.还是 I meant doing sth. 能不能i am interesting to do sth?为什么 那为什么可以是i am happy to do st 英语语法问题Sth be adj to do Sth.中do是什么成份啊?I am happy to do sth中,d be happy （about）doing sth .be happy to do sth.哪个对? I am here to do sth l am happy to do sth 怎么看句子成分 be happy to do sth和have a good time doing sth的区别 use sth doing sth还是use sth to do sth I want to do sth I would like to do sth I feel like doing st 英语语法常识I am happy to do sth中 To do sth 是主语补足语还是状语,还有,为什么有的句子中 mean to do sth/ mean doing sth expect to do sth还是doing sth?