The lab adds a 512 MiB spare disk, /dev/loop40, with an ext4 filesystem on it. It comes back at every boot. Task 2 changes the mount only until it's mounted again, so do the tasks in one go and run le-lab check before you clean up.

Tasks

Add /dev/loop40 to /etc/fstab by its UUID, mounted at /mnt/lab with the options defaults,noatime,noexec,nofail, and mount it from fstab.
Copy /usr/bin/true into /mnt/lab and show that it won't run from there. Then remount /mnt/lab so that programs can run from it, without changing /etc/fstab.
Make the mount busy (cd /mnt/lab), try to unmount it, and find the culprit with lsof. Not graded.

When le-lab check passes, remove your line from /etc/fstab, run systemctl daemon-reload and unmount, or leave it to le-lab reset.

Hints

blkid /dev/loop40, blkid -s UUID -o value.
After editing fstab: systemctl daemon-reload, mount -a, findmnt /mnt/lab.
mount -o remount,exec.
lsof +D /mnt/lab, fuser -vm /mnt/lab. Minimal RHEL-family installs need the lsof package.