I am sure to do it.其中to do it是不定式做这个句子的什么成分?

I am sure to do it.其中to do it是不定式做这个句子的什么成分? "It's sure to do"的“to do”在句子中做什么成份 I am willing to do sth 中不定式做什么成分?（关于一些句法） i can do it.这个do 做什么成分呢? I'm sure to do it myself I don’t know what to do 这是动词不定式做什么成分? I have to do the homewoek 这个句子中的不定式做什么成份?求解答 I followed it to see where it was going中不定式做什么成分 be sure to do的主语是人还是it? I am at a loss what to do 中what to do 做什么成分 it is never too old to learn.to learn不定式做句子什么成分? i have a lot of work to do to do是句子里的什么成分