Every possible means , but the teacher as well as the students found a solution to the problem yet.
A. has been tried; hasn’t
B. has tried; haven’t
C. have tried; haven’t
D. have been tried; hasn’t
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(答案→)A. has been tried; hasn’t
B. has tried; haven’t
C. have tried; haven’t
D. have been tried; hasn’t
解析：考查主谓一致。means单复同形，与every修饰，谓语动词用单数；as well as连接两个主语，谓语动词与前一个主语保持一致，故选A。