Final answer:
Franz Liszt, a prominent composer of the 19th century, was the individual among the listed options who had a known romantic relationship with George Sand, a French novelist.
Step-by-step explanation:
Aurore Dudevant, better known by her pseudonym George Sand, was a French novelist and memoirist who led a colorful and controversial life which included several romantic relationships. Among the notable individuals she had relationships with, Franz Liszt is one that had exchanged romantic affections with her. Liszt was a prominent composer and pianist of the 19th century, becoming a central figure in the Romantic movement in music. The leaders of Romanticism in other fields, such as Eugène Delacroix in painting, were contemporaries of Sand and Liszt but there are no records of romantic connections between Delacroix and Sand. Delacroix was known for his works such as "Liberty Leading the People" which remain iconic symbols of the French Romantic movement.