[单项选择题] 在窗体上画一个名称为Command1命令按钮，然后编写如下事件过程：Private Function fun1(n As Integer)As Integer Dim k As Int

[单项选择题] 在窗体上画一个名称为Command1命令按钮，然后编写如下事件过程：

Private Function fun1(n As Integer)As Integer

Dim k As Integer

If n = 1 Then

k = 1

Else

k = 1 + fun1(n - 1)* 2

End If

fun1 = k

End Function

Private Sub Command1_Click ()

Dim m As Integer, x As Integer

x = 4

m = fun1 (x)

Print m

End Sub

程序运行后，单击命令按钮，则窗体上显示的内容是

A．4

B．6

C．9

D．15