Junk messaging has been a headache for years, ＿＿the action taken by the authori-ties has not yet produced the results expected
A. as
B. but
C. so
D. before
网友回答
A. as
(答案→)B. but
C. so
D. before
解析：考查连词：句意：垃圾消息是多年以来一直让人头痛的事情，但是政府采取的行动还没有达到预想的效果。两句话是转折关系，用but，as正如，so因此，before在….前面，选B。