@Setanta,
Quote:I'd say that is the correct response,
I'd say that that is the dumbest thing that you've said in quite some time, Set.
Quote: and avoids using "single" twice.
Not that there's anything wrong with that.
Quote:I'd go further and say that that is how most native speakers of English would fill in the blank.
Okay, maybe I was a little hasty above - maybe it was the second dumbest thing that you've said in quite some time.
Obviously, it depends on what the speaker wants to say.