In case the file containing the Linux kernel is lost, what happens when the system is booting?

A. The system starts normally since the bootloader copies the kernel to the master boot record of the hard disk.
B. Instead of the kernel, the initramfs is loaded and instructed to mount the root filesystem and reinstall the kernel from the original package or from source.
C. The bootloader mounts the root filesystem read-only and launches /bin/sh directly in order to allow the administrator to reinstall the kernel.
D. Without a kernel a system cannot boot and, depending on the bootloader, an error is displayed.