Or, perhaps better, just let that hang for a moment - long enough to become uncomfortable - and then say "Try again." As others have said, if they can't or won

Or, perhaps better, just let that hang for a moment - long enough to become uncomfortable - and then say "Try again." As others have said, if they can't or won't get that that's unacceptable behavior, fire them. (jerf is more patient than I am...)