Answer
Contrary to the provided answer, El Lissitzky did, in fact, work in the medium of sculpture. He created numerous sculptures throughout his career, primarily in the Constructivist style. Among his notable sculptures are "Head of Proun" (1923) and "Monument to Lenin" (1925). While painting, graphic design, and architecture were undoubtedly central to his artistic practice, Lissitzky's body of work encompasses a wide range of media, including sculpture.