It is very nice of you后接to do 还是doing?

It is very nice of you后接to do 还是doing? it’s very nice （是用for 还是 of）you to do 请问,It is a waste of time 后该用to do 还是 doing It is a waste of money 后用to do还是 doing it is a waste of time doing还是to do it is better 后加to do还是doing It is really nice (of) you,it is important (for) you to do t It is very nice of you to help me 为什么要用of It is very nice ___ you to write to me.A.of B.on C.for it is very -------of you to write to me.A：nice B；better C：we it is nice doing和it is nice to do有什么区别 It is very nice of you为什么用of