is clear the Diaoyu islands have been China's inherent territory （固有领土）both from histori

问题补充：

is clear the Diaoyu islands have been Chinas inherent territory （固有领土）both from historical and legal aspects since ancient times．

A. That; that

B. This; this

C. It; that

D. What; what

答案：

A. That; that

B. This; this

(答案→)C. It; that

D. What; what

解析：考查形式主语句。本题的it是形式主语，真正的主语是that所引导的主语从句，that在句中不充当任何成分，只是一个引导词，没有任何的意思。句意:钓鱼岛自古以来就是中国的领土这一点是非常清楚的。故C正确。