The Green Knight swings his ax at Sir Gawain's head three times but only nicks him a bit on the third try. According to the Green Knight, why does he nick him on the third try?

This is Garwain's punishment for the pride he showed in accepting the challenge.

This is Gawain's punishment for not being truthful in exchanging the magic green belt that he believed would save his life.

This is enabling Gawain to return to King Arthur as a warning not to let his knights enter the Green Knight's territory.

This is Gawain's punishment for trying to seduce the lady of the house where he was staying.