The advertisementson the wall are designed by my sister.A. are put upB. are putting upC. p

问题补充：

The advertisementson the wall are designed by my sister.

A. are put up

B. are putting up

C. put up

D. be put up

答案：

A. are put up

B. are putting up

(答案→)C. put up

D. be put up

解析：句意：张贴在墙上的广告是由我妹妹设计的。该句的主语是The advertisements，已有谓语动词are designed，故填写在空白处的动词应与后面的on the wall一起构成定语修饰前面的名词，所以选C，过去分词短语作后置定语。