Question

It’s difficult     the math problem.

A .of him to work out   B. for him to work out

C. of him working out   D. for him working out

Answer

B

【解析】句意：对他来说算出这道数学题很难。It’s+ adj. + for/of sb. to do sth.做某事对于某人来说怎么样。首先排除C,D答案；如果形容词是修饰sb.的，也就是说能与sb.构成系表关系，就用介词of；如果形容词是修饰后面的动词不定式，就用介词for。此处的different不是修饰him的，而是做题难，要用介词for，故答案为B。

点睛：句型“It is+ adj.+ (for sb.) to do sth." 和“It is + adj.+(of sb.) to do sth."两个句型中，for sb.和of sb.怎么区别，在使用时要注意adj.是说明sb.的品质特点的还是说明to do sth.的就可以了，说明sb.的品质特点用of sb；说明to do sth.用for sb.如：

It’s very kind of you to help me. 你能帮我真好。（kind是修饰you，并且可以和you构成系表结构。）

It's very hard for him to study two languages. 对他来说，学两门外语是很难的。（kind是修饰后面的动词不定式的。）