Every means has been . No one is effective.A. trying outB. tried outC. trying inD. tried o

问题补充：

Every means has been . No one is effective.

A. trying out

B. tried out

C. trying in

D. tried on

答案：

A. trying out

(答案→)B. tried out

C. trying in

D. tried on

解析：词组辨析题。句意：每一种方法都尝试过了，没有一个有效。Try out 尝试，try on 试穿；根据语境可知“方法”是被“尝试”所以要用过去分词表被动。选B