Which film is considered as a representation of Fritz Lang's work and stylistic techniques?

Fritz Lang is renowned for his contributions to the cinematic landscape, particularly as a pioneer of German Expressionism and for his ability to fuse genres and explore complex themes. Among the listed films, "Metropolis" is widely recognized as a quintessential representation of Lang's work and stylistic techniques.

"Metropolis," released in 1927, exemplifies Lang’s mastery in combining innovative visual storytelling with intricate narrative structures. The film showcases his hallmark techniques, such as the use of dramatic lighting, elaborate set designs, and sophisticated special effects to create a dystopian future. It explores themes of class struggle, technology, and human emotion, all central to Lang's body of work.

In contrast, while "M" is also a significant film by Lang, it does not encapsulate the same level of grandeur and stylization as "Metropolis." The other options, "The Cabinet of Dr. Caligari" and "Nosferatu," are landmark films in their own right but are not associated with Lang; rather, they reflect the innovations of Robert Wiene and F.W. Murnau, respectively, who were contemporaries in the German Expressionist movement.