Final answer:
The poetic style that used rhythm and imagery to suggest moods or emotions is Symbolism. Symbolists focused on the mystical and spiritual, contrasting with the Realism and Naturalism movements that depicted objective reality.
Step-by-step explanation:
The poetic style that experimented with rhythm, sound, and the clustering of images to suggest moods or emotions is known as Symbolism (Option C). Symbolism emerged partly as a reaction against Realism and Naturalism, movements which represented the world pragmatically and objectively. In contrast, Symbolists aimed to express the mystical or spiritual aspects of experience. They were less concerned with portraying reality as it is, focusing instead on feelings, moods, and ideas evoked by the poetry. Symbolist poets like Charles Baudelaire and Arthur Rimbaud placed a heavy emphasis on rhythm, using it as a musical element to enhance the expressiveness of the poetry.
While Romanticism (Option B) was also characterized by an emphasis on emotion and the power of nature, it did not focus predominantly on the experimental use of sound and rhythm in the way that Symbolism did. Realism (Option A) and Classicism (Option D) are less concerned with mood and more focused on depicting reality and traditional forms respectively.