What happens when the Linux kernel can’t mount the root filesystem when booting?

A.
An error message is shown and the system reboots after a keypress.

B.
An error message is shown and the system boots in maintainence mode.

C.
An error message is shown, stating that the corresponding kernel module couldn’t be loaded.

D.
An error message is shown, showing which device couldn’t be mounted or informing that init couldn’t be found.

E.
An error message is shown and the administrator is asked to specify a valid root filesystem to continue the boot process.

Explanation:
Some Required information to Boot loader is boot partition, root partition, kernel file, initrd image file. If Kernel unable to mount the /filesystem, it shows error like mount: error 15 mounting ext3 mount: error 2 mounting none switchroot: mount failed: 22 umount/initrd/dev/: 2 Kernel Panic: no syncing: Attempted to kill init! This error occurred in your system before showing welcome redhat linux. That means problem in grub boot loader.