单击一次命令按钮，下列程序代码的执行结果为( )。 Private Sub Commandl_Click() Dima As Integer,b As Integer，CASInteger a=2：b=3：c=4 PrintP2(c，b，a) End Sub PrivateFunctionPl(X As Integer,y As Intege；z As Integer)P1=2*x+y+3*Z End Function PrivateFunctionP2(X As Integer,y As Integer,z As Integer)P2=P1(z,x,y)+x End Function

A．21

B．19

C．17

D．34