Which of the following poems is associated with themes of nature and mourning in Whitman's work?

The chosen poem, "When Lilacs Last in the Dooryard Bloom'd," intricately weaves themes of nature and mourning, making it a powerful reflection on loss. Written in response to the death of President Abraham Lincoln, the poem employs natural imagery, particularly the lilacs, the star, and the birds, to convey profound grief and reflection. The blooming of the lilacs serves not only as a symbol of beauty and life but also as a poignant reminder of mortality and the cycle of nature, emphasizing the interplay between life and death.

In contrast, "Song of Myself" explores a wide array of themes, including individuality and the self but does not focus primarily on mourning. "A Noiseless Patient Spider" uses the spider as a metaphor for the soul and its search for connection, leading to themes of isolation rather than direct mourning. "Crossing Brooklyn Ferry" examines the interaction between the individual and collective experience, emphasizing shared moments rather than a specific theme of mourning. Thus, "When Lilacs Last in the Dooryard Bloom'd" stands out for its unique combination of natural elements and deep emotional resonance related to loss.