A:When was it
B:It was when that
C:It was whe
D:When it was that
在平面直角坐标系中,已知点E(﹣4,2),F(﹣2,﹣2),以原点O为位似中心,相似比为2:1,把三角形EFO缩小,则点E的对应点E′的坐标是( )
影响人口迁移的因素中,主要的、经常起作用的因素是( )