单项选择题

有如下函数:Private Function firstfunc(x As Integer, y As Integer) As Integer Dim n As Integer Do While n <= 4 x=x +y n=-+1 Loop firstfunc = x End Function调用该函数的事件过程如下:Private Sub Command1_lick() Dim x As Integer Dim y As Integer Dim n As Integer Dim z As Integer x=1 y=1 For n = 1 To 3 z = firstfunc(x, y) Next n Print z End Sub该事件过程的执行结果是 ______。

A.1
B.3
C.16
D.9