----Can he work out the maths problem?--I think hard for him to work it out.A. it’sB.

问题补充：

----Can he work out the maths problem?

----I think hard for him to work it out.

A. it’s

B. that’s

C. this is

D. they’re

答案：

(答案→)A. it’s

B. that’s

C. this is

D. they’re

解析：本题考查的是it’s +adj +for sb do sth，故选答案为A