The lines you've quoted from John Keats' "La Belle Dame sans Merci" exemplify C: the hero's temptation to become distracted from his quest.
In the poem, the knight-at-arms experiences a profound distraction due to his enchantment with the beautiful lady. His focus shifts from his noble duties to the allure of love and desire, leading to his eventual downfall and melancholy as he becomes entrapped in her enchanting world. The references to dreaming and the appearance of pale kings and warriors signal the consequences of this distraction and the loss of his former purpose.