The /var partition is 100% full, which can lead to system instability (e.g., logging failures, package manager issues).
* C is correct: lvextend -L +5G -r increases the size of the logical volume and resizes the filesystem in one command. This is the safest and most effective way to address space issues without data loss.
Incorrect Options:
* A: Reformatting /var with mkfs.xfs will erase all data - destructive and unnecessary.
* B: Removing all files from /var is highly dangerous as it contains logs, spool files, caches, and more.
Critical system components will be lost.
* D: Resizes the wrong logical volume - / not /var.
Reference:
CompTIA Linux+ XK0-005 Official Study Guide, Chapter 7
man lvextend
man df

The high number of errors and dropped packets in the output of the network interface counters indicate a connection problem on the network interface.
Reference:
CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 10: Managing Networking, Section: Troubleshooting Network Issues, Page 359.
Linux+ (Plus) Certification, Exam Objectives: 4.3 Given a scenario, troubleshoot and resolve basic network configuration and connectivity issues.

The command docker images prune -a will help to remove all dangling images and delete all the images that do not have an associated container. The docker command is a tool for managing Docker containers and images. The images subcommand operates on images. The prune option removes unused images. The - a option removes all images, not just dangling ones. A dangling image is an image that is not tagged and is not referenced by any container. This command will accomplish the task of cleaning up the unused images.
The other options are incorrect because they either do not exist (docker push images -a or docker images rmi -- all) or do not remove images (docker rmi -a images only removes images that match the name or ID of
"images"). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Cloud and Virtualization Technologies, page 567.

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.