Over the past decades forest area in China as a result of massive deforestation.A. had d

问题补充：

Over the past decades, forest area in China as a result of massive deforestation.

A. had decreased

B. decreased

C. is decreasing

D. has been decreasing

答案：

A. had decreased

B. decreased

C. is decreasing

(答案→)D. has been decreasing

解析： 考查时态。Over the past+时间段，用现在完成时态，故选D。