单项选择题

下面程序：

Private Sub Form_Click()

Dim x,y,z As Integer

x=5

y=7

z=0

Call P1(x,y,z)

Print Str(z)

End Sub

Sub P1(By Val a As Integer, By Val b As Integer, c As Integer)

c=a+b

End Sub

运行后的输出结果为______。

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