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The dd command can be used to create a new file that is 100kB in size. The dd command copies data from one source to another, using specified input and output block sizes. To create a new file that is 100kB in size, the dd command can use /dev/zero as the input source, which provides an endless stream of zeros, and specify the output file name, the output block size (bs) and the count of blocks to copy. For example, dd if=/dev/zero of=file.txt bs=1k count=100 will create a file named file.txt that is 100kB in size. The file command can be used to determine the type of a file. The mkfile command is not a valid Linux command. The touch command can be used to create a new empty file or update the access and modification times of an existing file, but it does not specify the size of the file. References: [LPI Exam 101 Detailed Objectives],Topic 103: GNU and Unix Commands, Weight: 25, Objective 103.3: Perform basic file management, dd command, file command, touch command

 The correct file permissions that belong to a symbolic link are lrwxrwxrwx. This is because a symbolic link is a special file that points to another file or directory. The first character of the file permissions indicates the file type. The letter l means that the file is a symbolic link. The other letters r, w, and x represent the read, write, and execute permissions for the owner, group, and others classes. However, the permissions of the symbolic link are not used for accessing the file or directory that it points to. The permissions of the target file or directory are used instead. Therefore, the permissions of the symbolic link are usually set to rwx for all classes, meaning that anyone can read, write, or execute the link. The other options are incorrect because they do not indicate the file type of a symbolic link. Option A is wrong because the first character - means that the file is a regular file, not a symbolic link. Option B is wrong because the first character + is not a valid file type indicator. Option D is wrong because the first character s means that the file is a socket, not a symbolic link. References:

• symlink - Change permissions for a symbolic link - Unix & Linux Stack Exchange
• linux - How do file permissions apply to symlinks? - Super User
• Is it possible to change the permissions for the symbolic link?
• Permission through symbolic link - Unix & Linux Stack Exchange
• How to change permissions for a symbolic link under Linux/UNIX

 The common Linux commands for file management are mv, cp and mkdir. The mv command moves or renames files and directories. The cp command copies files and directories. The mkdir command creates directories. The copy and move commands are not valid Linux commands. References:

• LPI Exam 101 Detailed Objectives, Topic 103: GNU and Unix Commands, Weight: 25, Objective 103.1: Work on the command line
• LPI Linux Essentials Study Guide, Chapter 3: Working on the Command Line, Section 3.2: Basic Commands, Page 55

The command mount -a mounts all filesystems that are listed in the file /etc/fstab and have the option auto set. The option auto means that the filesystem can be mounted automatically by the mount -a command or at boot time. The option noauto means that the filesystem can only be mounted explicitly by the mount command with the device or mount point specified12. The file /etc/fstab containsinformation about the filesystems that are known to the system and how they can be mounted3. The command mount -a is useful for mounting all the filesystems that are needed by the system after a change in /etc/fstab or after a reboot4. References: 1: mount(8) - Linux man page 2: Linux mount and umount commands help and examples 3: fstab(5) - Linux man page 4: How to Use the mount Command on Linux