You have created a Systemd mount unit file that mounts a filesystem upon entering the multi$-$user target. However, when you switch to the multi$-$user target, you notice that the filesystem is not mounted. Which of the following troubleshooting steps should you take? $($Choose all that apply.$)$

a$.$ Verify that the filesystem was specified using a UUID in the mount unit file.

b$.$ Remove any entries for the filesystem from $/$etc$/$fstab$.$

c$.$ Ensure that the mount unit is activated using the systemctl enable command.

d$.$ Run the update$-$rc$.$d command to reindex all unit files.