"df" shows space, but the storage is in fact ran out of space. This is usually due to a file that was deleted but a process is still has the file opened an it will not release the space until the process is killed or restarted. The first step to fix this issue is to find the process that is opening deleted files and "lsof" is the best tool to find that.

if the script finds company A, the result should be equal to 0.

The list of commands in option D is the correct way to achieve the goal. The commands are as follows:
* fallocate -l 1G /ops/app.img creates a 1GB file named app.img under the /ops directory.
* mkfs.xfs /ops/app.img formats the file as an XFS filesystem.
* mount -o loop /ops/app.img /ops/app mounts the file as a loop device under the /ops/app directory. The other options are incorrect because they either use the wrong commands (dd or truncate instead of fallocate), the wrong options (-t or -f instead of -o), or the wrong order of arguments (/ops/app.img
/ops/app instead of /ops/app /ops/app.img). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 10: Managing Storage, pages 323-324.

Explanation
The command fsck.ext4 /dev/sda1 can be used to address the issue. The issue is caused by a corrupted filesystem on the /dev/sda1 partition. The error message shows that the filesystem type is ext4 and the superblock is invalid. The command fsck.ext4 is a tool for checking and repairing ext4 filesystems. The command will scan the partition for errors and attempt to fix them. This command can resolve the issue and allow the system to start. The other options are incorrect because they either do not fix the filesystem (partprobe or fdisk) or destroy the data on the partition (mkfs.ext4). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 10: Managing Storage, page 325.