单击一次命令按钮之后，下列程序代码的执行结果为______ 。 Private Sub Command1_ Click()a = fun(4) + fun(5)Print a; End Sub Public Function fun (n As Integer)Static NumFor i = 1 To n Num = Num + iNext ifun = Num End Function

A．15

B．20

C．35

D．40