B. thoughtful
The tone of this poem is thoughtful. The poem begins with the image of the speaker floating like a cloud in the sky and seeing a field of daffodils. The speaker describes the field of daffodils with positive words such as "fluttering", "dancing", "twinkle" and "sprightly". This gives the poem a positive tone thus eliminating the negative answer choices of dejected and overwhelmed. The last stanza of the poem explains that the speaker is lying on the couch in "vacant or in pensive mood". Pensive is another word for thoughtful, so thoughtful is the best choice.