We all feel it is you as well as your wife that for your son’s bad performance at school.

问题补充：

We all feel it is you as well as your wife that for your son’s bad performance at school.

A. are to blame

B. is to blame

C. are to be blamed

D. is to be blamed

答案：

(答案→)A. are to blame

B. is to blame

C. are to be blamed

D. is to be blamed

解析：as well as连接两个并列主语，谓语动词要和前一主语保持一致，blame不用被动语态，常用be to blame结构，故本题选A。