Answer:
I believe the answer to be lines 12 and 14: "tossing their heads in sprightly dance" and "Out-did the sparkling waves in glee", respectively.
Step-by-step explanation:
William Wordsworth wrote this poem after spending an afternoon walking with his sister. While walking, he came across a field full of daffodils. The memory of such scenery made quite an impression on the poet and, in this poem, he says the vivid memory of that afternoon still fills his heart with joy.
The lines that seem to best show his awe for nature are the ones describing the daffodils: the way they dance in the wind, lively, forming waves more beautiful and sparkling than the waves in the ocean.