The best response to the question is:
The soft snowy wind and loveliness of the forest creates a peaceful and sleepy mood as the speaker appreciates the scenery.
This choice captures the serene atmosphere conveyed in stanzas 3 and 4, where the imagery of the quiet woods, the gentle sound of the wind, and the beauty of the snow contributes to a tranquil and reflective mood. The speaker's moment of contemplation amidst the lovely, dark, and deep woods enhances this sense of peace, despite the underlying acknowledgment of responsibilities symbolized by the repeated lines about having "promises to keep."