单项选择题

在窗体上画一个命令按钮,然后编写如下程序:   Private Sub Commandl_Click( )     Dim a AS Integer,b As Integer     a=15     b=2     t N(a,b)   End Sub   Function N(x As Integer,y As Integer) As Integer     N=IIf(x)y,x,y)   End Function   程序运行后,单击命令按钮,输出结果为( )。

A.20
B.261
C.15
D.25