Every means tried, yet no result encouraging up to now.
A. have been ...is
B. has been...has been
C. have ...has been
D. has...is
网友回答
A. have been ...is
(答案→)B. has been...has been
C. have ...has been
D. has...is
解析：考查时态及主谓一致。句意：每一种方法都试过了，到目前为止还没有令人鼓舞的结果。结合语境可知前文描述的是现在已经完成的动作，故用现在完成时态。主语为抽象名词不可数，故谓语动词用单数。下文根据时间状语可知也是现在完成时态，主语result同样是抽象名词，故谓语动词也用单数，选B。