A:have been to
B:has been to
C:has gone to
D:have gone to
+Q和﹣Q是两个等量异种点电荷,以点电荷+Q为圆心作圆,A,B为圆上两点,MN是两电荷连线的中垂线,与两电荷连线交点为O,下列说法正确的是( )
隋朝政权的基础是( )
仿写词语
绿油油____ ____ ____ ____