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

A．AABB

B．BBAA

C．AA

D．BB

临床上85%～90%的颅内动脉瘤位于前循环，后循环动脉瘤常见于（）

A.桥脑动脉

B.小脑后下动脉和基底动脉尖

C.小脑上动脉

D.枕动脉

E.小脑前下动脉