单击一次命令按钮，下列程序代码的执行结果为( )。
Private Sub Command1_Click()
Dim a As Integer,b As Integer,c As Integer
a=2:b=3:c=4
Print P2(c,b,

A．
End Sub
Private Function P1(x As Integer,y As Integer,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(z,x,y)+x
End FunctionA) 21
B．19
C．17
D．34