Question

It's polite____the old.We should learn from you.

It's polite____the old.We should learn from you.
A.of you to help
B.for you to help
C.of you helping
D.for you helping 要有原因

Answer 1

A
你帮助老人真有礼貌。我们应该向你学习。

it is +adj+for+sb+to+do+sth和 it is+adj+of+sb+to+do+sth的区别

用of 的话，adj就用来形容sb的。即形容词是描述不定式行为者的性格、品质的，如kind，good，nice，right，wrong，clever，careless，polite，foolish等，用of sb.。故可以换成 sb is adj to do
比如：it‘s nice of you to help
me.=you are nice to help me.
1 It’s very kind of you to help me. 你能帮我，真好。
2 It’s clever of you to work out the
maths problem. 你真聪明，解出了这道数学题。

加油！不明白再问！如果帮到你，请采纳，谢谢！

Answer 2

选A。
It's polite__of you to help__the old.We should learn from you.

追问

原因呢？