在窗体上画一个名称为Command1的命令按钮，然后编写如下事件过程：
　Private Sub Command1_Click()
　　x = -5
　　If Sgn(x) Then
　　　y = Sgn(x ^ 2)
　　Else
　　　y = Sgn(x)
　　End If
　　Print y
　End Sub
　程序运行后，单击命令按钮，窗体上显示的是
A) -5
B) 25
C) 1
D) -1

A) 命令按钮的默认属性为Caption
B) 标签的默认属性为Caption
C) 复选框的默认属性为Value
D) 滚动条的默认属性为Value

A) Private Sub Form_MouseDown(Button AS Intege, _Shift As Integer, X As Single, Y As Single)
If Button=1 And Button=2 Then
PopupMenu a1
End If
End Sub
B) Private Sub Form MouseDown(Button As Integeg_Shift As Integer, X As Single, Y As Single)
PopupMenu a1
End Sub
C) Private Sub Form MouseDown(Button As Intege_Shift As Integeg, X As Single, Y As Single)
If Button=1 Then
PopupMenu a1
End If
End Sub
D) Private Sub Form_MouseDown(Button As Integer, _Shift As Integer, X As Single, Y As Single)
If Button=2 Then
PopupMenu a1
End If
End sub