Explanation
The command mount -a ensures that all file systems listed with the option auto in /etc/fstab are mounted. The
/etc/fstab file contains the information about the file systems that can be mounted automatically or manually.
The option auto means that the file system can be mounted automatically at boot time or when the command mount -a is issued. The option noauto means that the file system can only be mounted manually by specifying the device or mount point. The command mount -a ignores the file systems with the noauto option and mounts the rest of the file systems that are not already mounted. The other options are incorrect because they do not describe the correct behavior of the command mount -a. Option A is wrong because the command mount -a ignores the file systems with the noauto option. Option B is wrong because the command mount -a does not show any output, unless the -v option is used. To show the mounted file systems, the command mount without any arguments can be used. Option C is wrong because the command mount
-a does not open any editor. To edit the /etc/fstab file, a text editor such as vi, nano, or gedit can be used.
Option E is wrong because the command mount -a does not mount all file systems listed in /etc/fstab, but only those with the auto option. References:
* [LPI Linux Essentials - 2.2 Mounting, Unmounting Filesystems]
* Linux mount Command with Examples - phoenixNAP
* How does the Linux command "mount -a" work? - Unix & Linux Stack Exchange
* mount command in Linux with Examples - GeeksforGeeks
* mountLinux