首先提出了预期的环境政策的文献是（）。
参考答案：《世界自然资源保护大纲》
小麦是重要的粮食作物，在我国北方大面积种植，是一年生草本植物。 [ ]
My book was here a second ago but now it's missing. Someone _____ a joke on me.[ ]
A. must be playing
B. must play
C. can't have played
D. can't play
