以下程序运行后，单击命令按钮，窗体显示的结果是 ______。 Private Function p1(x As Integer，y As Integel，z As Integer) p1=2*x+y+3*z End Function Private Function p2(x As Integer，y As Integer，z As Integer) p2=p1(2，y，x)+x End Function Private SubCommandl_Click() Dim a As Integer Dim b As Integer Dim c As Integer a=2:b=3:c=4 Print p2(c，b，
A．
End SubA) 19
B．21
C．22
D．23