be useful to是加do还是加ing?

be useful to是加do还是加ing? be加过去分词后面加to do 还是do? be hard后加to do 还是加doing be better加什么是to do 还是do used to和be use to 加do还是doing attend后面跟名词时要不要加冠词be adj 是to还是for sbkind friendly之类的是to,那么good useful之类的呢 be busy加什么?be busy是接doing sth还是to do sth? to believe 还是 to be believe 为什么还有个be to do believe 是动词 为什么还加be be supposed to do sthbe supposed to 加动词原形,还是be supposed 加动词不定式 find后面是加do还是加doing还是加to do? look forward to是加doing还是加do? difficult是加动词ing?还是加to do sth. be accustomed to后面加do sth.还是doing sth? against 加doing 还是to do ,against 前要加 be be different from后加to do 还是doing be used to后面加do还是doing be ashamed to后加do 还是doing hope加doing还是加to do