The mother didn't know who for the broken glass as it happened.
A. to blame
B. to be blamed
C. blamed
D. is to be blamed
网友回答
(答案→)A. to blame
B. to be blamed
C. blamed
D. is to be blamed
解析：考察特殊结构。特殊结构“特殊疑问词+to do sth”可以在句中作主语，宾语，表语甚至定语。同时固定搭配be to blame该受责备，使用主动语态表示被动含义。本句指的who to blame作为动词know的宾语。句意：当杯子坏掉的时候妈妈不知道该责备谁。个A正确。