The final four stanzas of John Keats' poem "La Belle Dame sans Merci" serve multiple purposes, but the most fitting answer among the choices provided is:
D. The knight finally answers the question posed in the beginning of the poem.
In the earlier stanzas, the speaker asks the knight what is troubling him. The last four stanzas reveal the knight's experience with the mysterious lady, his subsequent enchantment, and the curse he now bears, thus providing clarity and resolution to the initial question about his plight.