9. Double-Check Everything

A: I have to go back upstairs.

B: Why? We're already late.

A: I have to check the stove.

B: What's the matter?

A: Maybe I left the burner on.

B: No, you didn't. I checked the stove before we left.

A: Are you sure?

B: Of course I'm sure.

A: Well, I have to go back upstairs anyway.

B: It's getting later every minute.

A: I think I left the water running.

B: No, you didn't. Let's go! The only thing running is the clock!