It is very kind you to help me with my lessons. It is difficult me to learn them well.A.

问题补充：

It is very kind you to help me with my lessons. It is difficult me to learn them well.

A. of , of

Bfor , of

C. of , for

D. for , for

答案：

A. of , of

B. for , of

(答案→)C. of , for

D. for , for

解析：考查固定句型。It is +adj. of/for sb. to do sth.当形容词是指人时，用介词of；指物时用介词for。Kind“友好的”，指人，故用of；排除B、D；difficult“困难的”，指事情，用for。故选C。