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(ByVal a As Integer，ByVal b As Integer,c As Integer)
c=a+b
End Sub
运行后的输出结果为 ______。

点击查看答案&解析