Final answer:
The lines that best illustrate joy found in nature are about daffodils dancing by the lake, the poet's happiness in their company, and the memory of this joy bringing pleasure in solitude.
Step-by-step explanation:
The lines from the poem that best shape the theme that joy can be found in experiencing the natural world are:
- "Beside the Lake, beneath the trees, / Fluttering and dancing in the breeze."
- "A Poet could not but be gay, / In such a jocund company:"
- "For oft, when on my couch I lie / In vacant or in pensive mood, / They flash upon that inward eye / Which is the bliss of solitude;"
These lines exemplify the joy and emotional wealth the poet derives from recalling the sight of daffodils by the lake and how this memory brings happiness in moments of solitude. The expression "A Poet could not but be gay" directly relates to the emotion of joy inspired by nature's display. Furthermore, the lines highlight the Romantic period's value of finding deep emotional connections and spiritual replenishment in the beauty and peacefulness of the natural surroundings.