Final answer:
Sir Gawain stands perfectly still as the Green Knight brings down his axe.
Step-by-step explanation:
As the Green Knight brought down his axe, Sir Gawain stands perfectly still. He does not flinch or move. This is because Sir Gawain has accepted the challenge of the Green Knight and is determined to prove his bravery and honor. By standing still, Sir Gawain shows his courage and readiness to face whatever consequences come his way.