What will be displayed when the button is clicked on?

```
Private Sub btnDisplay_Click(...) Handles btnDisplay.Click
Dim x, y As String
x = "tin"
y = "can"
Swap(x, y)
txtOutput.Text = x & " " y
End Sub
Sub Swap(ByRef x As String, y As String)
Dim temp As String
temp = x
x = y
y = temp
End Sub
```
(A) tin can
(B) can tin
(C) tin tin
(D) can can

(D) can can