they're very kind of you对吗
问题描述：
they're very kind of you对吗
答
同意楼上的答案.
It's +adj.+of sb to do sth是一个固定用法,of后面跟的是人的品质的形容词.
对比另外一个类似用法：It's It's +adj.+for sb to do sth,for后面跟的不是表示人的品质的形容词.