is a growing world problem, and nowadays the United Nations and its member countries hard to deal with it．
A. Desertification; are working
B. Desertified ; worked
C. Desert; work
D. Desertification; have worked
网友回答
(答案→)A. Desertification; are working
B. Desertified ; worked
C. Desert; work
D. Desertification; have worked
解析：
第一空填：Desertification“沙漠化”，第二空考时态：句意是：沙漠化是日益严重的世界问题，现在联合国和成员国正努力对付它。用现在进行时，选A。