To allow a regular user account to mount and unmount a filesystem (for instance, a cdrom or floppy), which of the following options will need to be added to the corresponding line in /etc/fstab?

`nouidchk` is an NFS mount option related to UID checking, not to enabling regular users to mount local filesystems.

`alluser` is not a valid or recognized mount option for `/etc/fstab` to allow user mounting.

The `user` option in `/etc/fstab` grants any regular user the ability to mount and subsequently unmount the specified filesystem, typically used for removable media devices like CD-ROMs or USB drives.

`auto` ensures the filesystem is mounted automatically at boot or with `mount -a`, but it does not confer permissions for regular users to manually mount or unmount it.