During the last three minutes of a half, the penalty for failure to place the ball in play within the 20-second play clock, known as "time count" (this foul is known as "delay of game" in American football), is dramatically different from during the first 27 minutes. Instead of the penalty being 5 yards with the down repeated, the base penalty (except during convert attempts) becomes loss of down on first or second down, and 10 yards on third down with the down repeated. In addition, as noted previously, the referee can give possession to the defence for repeated deliberate time count violations on third down.

Answer this question, if possible (if impossible, reply "unanswerable"): On what down can the 20 second play clock give possession to the defense?
unanswerable