The correct answer is B.
Near the end of the play, the spirits tell Macbeth that he cannot be harmed by any man born of woman and he will be safe until Birnam Wood comes to Dunsinane Castle.
Believing none of this two events could ever take place, Macbeth relaxes.
However, the predictions were misleading since while advincing to attack the castle, the English disguised itself with branches and boughs from Birnam Wood and and Macduff was not born of woman but “untimely ripped” from his mother’s womb.