有如下函数:Private Function firstfunc(x As Integer, y As Integer) As IntegerDim n As Integer Do While n ＜= 4x=x +yn=-+1 Loopfirstfunc = 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