单项选择题

窗体上有一个图片框和一个命令按钮(拖动模式为自动)，执行程序后，拖动按钮经过图片框时输出结果为
Private Sub Picture1_DragOver(Source As Control, X As Single, Y As Single, State As Integer)
Static a As Boolean
If Not a Then
Print"AA"
a=True
End If
End Sub
Private Sub Picture1_MouseMove(Button As Integer, Shift As Integer, X As Shingle, Y As Single)
Static b As Boolean
If Not b Then
Print"BB"
b=True
End If
End Sub