This machine was used-----years ago.A. five hundredB. five hundredsC. five hundreds ofD

问题补充：

This machine was used -------years ago.

A. five hundred

B. five hundreds

C. five hundreds of

D. five hundred of

答案：

(答案→)A. five hundred

B. five hundreds

C. five hundreds of

D. five hundred of

解析：表示具体的数量可用数词+名词，数词不可使用复数，故本题选A。意思为五百年前。