Over the past decades , sea ice in the Arctic as a result of global warming .
A. had decreased
B. decreased
C. has been decreasing
D. is decreasing .
网友回答
A. had decreased
B. decreased
C. has been decreasing
D. is decreasing .
解析：
此题考查动词时态，由句中的时间状语从句“over the past decades”，可知句子的谓语动词要用现在完成时或现在完成进行时态。