He has read many books on history so it’s for him to answer these questions.A. hardB. im

问题补充：

He has read many books on history, so it’s for him to answer these questions.

A. hard

B. impossible

C. easy

D. serious

答案：

A. hard

B. impossible

(答案→)C. easy

D. serious

解析：hard困难的，努力的；impossible不可能的；easy容易的，简单的；serious严重的，认真的。句意：他读了许多历史书，因此回答这些问题对他来说很简单。故选C。