Teacher: Whose is this bag? Is it yours, Sally?

Sally: No, it isn't my bag. I think it's Mark's.

Mark: Yes, it's mine. And the jacket's mine, too.

Teacher: OK. And whose are these crisp bags and bottles?

Mark: They're note mine! They're Sally's.

Sally: No, they aren't! Tim was eating crisps!

Tim: Well, yes, they are mine. Sorry.

Teacher: Will you throw them away now, please?

Tim: Yes, sure.