单项选择题

在窗体上画一个名称为Command1的命令按钮和一个名称为Text1的文本框，然后编写如下程序：
Private Sub Command1_Click()
Dim x, y, z As Integer
x = 1:y = 2:z = 3
Text1. Text= " "
Call P1(x, y, z)
Text1.Text = Str(z)
End Sub
Sub P1 (ByVal a As Integer, ByVal b As Integer, c As Integer)
a= a + b
b= b + c
c= a + b
End Sub
程序运行后，单击命令按钮，则在文本框中显示的内容是

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