In the ring protection model shown here, what ring contains the operating system's kernel?

The kernel lies within the central ring, Ring 0. Conceptually, Ring 1 contains other operating system components. Ring 2 is used for drivers and protocols. User-level programs and applications run at Ring 3. Rings 0 through 2 run in privileged mode, while Ring 3 runs in user mode. It is important to note that many modern operating systems do not fully implement this model.