is known to us he is the top student of our class.A. ItB. AsC. ThisD. That

问题补充：

is known to us, he is the top student of our class.

A. It

B. As

C. This

D. That

答案：

A. It

(答案→)B. As

C. This

D. That

解析：考查非限制性定语从句。此处as代替he is the top student of our class.句意：他是我们班里的优秀学生，这一点我们都知道。如果用A项句型It is known to us that-----.