下列程序运行后，单击命令按钮，窗体显示的结果为( )。 Private Function pl(x As Integer,y As Integer,z As Integer) pl=2*x+y+3*z End Function Private Function p2(X As Integer,y As Integer,z As Integer) p2=p1(z,y,x)+x End Function Private Sub Commandl_Click()

A．23

B．19

C．21

D．22