Answer:
One line that enhances the theme of "Lines Written in Early Spring" by William Wordsworth is:
"And 'tis my faith, that every flower
Enjoys the air it breathes."
This line speaks to the idea of the interconnectedness of all things in nature and the importance of appreciating and respecting the natural world. The poem as a whole celebrates the arrival of spring and the renewal of life, while also acknowledging the darker aspects of human experience and the need for empathy and compassion.