In the past decades, sea ice in the Arctic as a result of global warming.
A. had melted
B. has been melting
C. melted
D. is melting
网友回答
A. had melted
(答案→)B. has been melting
C. melted
D. is melting
解析：考查时态。根据时间状语in the past decades在过去的几十年，说明一直到现在，并有可能继续持续下去，故用现在完成进行时。句意：在过去的几十年，由于全球变暖的原因，北极圈的海洋冰块一直在融合。故B正确。