Over the past decades sea ice in the Arctic as a result of global warming .A. had decrea

问题补充：

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 .

答案：

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。