The correct option to pass to a filesystem’s entry in /etc/fstab in order to mount the file system without root privileges is:

D. user

The /etc/fstab file is a configuration file that contains information about the filesystems on a Linux system. The /etc/fstab file defines how and when the filesystems are mounted by the mount command or the system. The /etc/fstab file has six fields for each filesystem entry, separated by whitespace. The fields are:

device: the device name or the UUID of the filesystem

mountpoint: the directory where the filesystem is mounted

type: the filesystem type, such as ext4, xfs, vfat, etc.

options: the mount options that modify the behavior of the mount operation, such as ro, noauto, user, etc.

dump: a flag that indicates whether the filesystem should be backed up by the dump command, 0 for no and 1 for yes

pass: a flag that indicates the order of filesystem checks by the fsck command at boot time, 0 for no check, 1 for root filesystem, and 2 or higher for other filesystems

The user option is a mount option that allows any non-root user to mount the filesystem. By default, only the root user can mount filesystems, unless they are specified in the /etc/fstab file with the user option. For example, to allow any user to mount a USB drive with the device name /dev/sdb1 to the directory /mnt/usb, the /etc/fstab entry would look like:

/dev/sdb1 /mnt/usb vfat user 0 0

The user option also implies the noexec, nosuid, and nodev options, which prevent the execution of binaries, the setuid and setgid bits, and the device files on the mounted filesystem, respectively. These options can be overridden by using the exec, suid, and dev options after the user option.

The other options are not correct because:

A. auto: This option indicates that the filesystem should be mounted automatically by the mount -a command or at boot time. This option does not affect the ability of non-root users to mount the filesystem. By default, all filesystems in the /etc/fstab file have the auto option, unless they are explicitly marked with the noauto option.

B. norestrict: This option does not exist in the mount command or the /etc/fstab file. There is no such option as norestrict in the Linux documentation or the man pages.

C. noauto: This option indicates that the filesystem should not be mounted automatically by the mount -a command or at boot time. This option does not affect the ability of non-root users to mount the filesystem. The noauto option is usually used for removable devices or network shares that are only mounted on demand.