单项选择题
有一个名称为Form1的窗体,上面没有控件,设有以下程序(其中方法Pset(X,Y)的功能是在坐标X,Y处画一个点):
Dim cmdmave As Boolean
Private Sub Form_MouseDown(Button As Integet, Shift As Integer, X As Single, Y As Single)
cmdmave=True
End Sub
Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If cmdmave Then
Form1.Pset(X, Y)
End If
End Sub
Private Sub Form_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
cmdmave=False
End Sub
此程序的功能是______。
A.每按下鼠标键一次,在鼠标所指位置画一个点
B.按下鼠标键,则在鼠标所指位置画一个点;放开鼠标键,则此点消失
C.不按鼠标键而拖动鼠标,则沿鼠标拖动的轨迹画一条线
D.按下鼠标键并拖动鼠标,则沿鼠标拖动的轨迹画一条线,放开鼠标键则结束画线