A:BamHI和EcoRI
B:BamHI和HindⅢ
C:EcoRI和HindⅢ
D:BamHI和BglII
在森林生态系统中,兔和鼠吃草,兔常被狐和鹰捕食,鼠常被狐和蛇捕食,蛇有时也被鹰捕食,这些现象可以说明动物在生物圈中的重要作用是( )
The________expression on his face suggested that he was________at the extraordinary beauty of the picture.