Do you know Australia was as a matter of fact used to be a nation of prisoners?A. whatB.

问题补充：

Do you know Australia was, as a matter of fact, used to be a nation of prisoners?

A. what

B. where

C. which

D. that

答案：

(答案→)A. what

B. where

C. which

D. that

解析：考查名词性从句。句意“事实上，你知道吗？澳大利亚曾经是囚犯之国。”表语从句缺少主语，用what充当be的byuv.gu选A。