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

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  .

试题答案

 D

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。