be happy to do sth

be happy to do sth be happy to do sth中的sth是什么意思 be happy （about）doing sth .be happy to do sth.哪个对? be happy/surprised to do sth后面这个to do sth充当着什么语? be happy to do sth和have a good time doing sth的区别 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 let to do sth be surprised to do sth be able to do sth be obliged to do sth. be going to do sth be willing to do sth