—What’s this?—It’s a machine which was invented in century in China.A. sixB. sixthC. the

问题补充：

—What’s this?

—It’s a machine which was invented in century in China.

A. six

B. sixth

C. the six

D. the sixth

答案：

A. six

B. sixth

C. the six

(答案→)D. the sixth

解析：

试题分析: 句意：那是什么？是个在中国六世纪发明的机器。 six六，sixth第六。century世纪，前用序数词，序数词前用定冠词，故选D.