单项选择题

下面程序：
Private Sub Form_Click()
Dim x,y，z As Integer
x=5
y=7
2=0
Call P1(x,y，z)
Print Str(z)
End Sub
Sub P1(By Va1 a As Integer，By Va1 b As Integer，c As Integer)
c=a+b
EndSub
运行后的输出结果为_________。