Two Birds,vacuum extruder

[align=left]Teacher: Here are two birds, one is a swallow, and the other is a sparrow. Now who can tell us which is which?[/align][align=left]　　Student: I cannot point out, but I know the answer.[/align][align=left]　　Teacher: Please tell us.vacuum extruder[/align][align=left]　　Student: The swallow is beside the sparrow and the sparrow is beside the swallow.[/align]