The correct answer is D. /etc/fstab.
/etc/fstab is a system configuration file that contains information about the filesystems that are mounted on a Linux system. It is used to specify the location of the filesystem, the type of filesystem, the mount point, and other options.
A. /etc/mount.sys is not a valid file.
B. /etc/filesys is not a valid file.
C. /etc/sysconfig is a system configuration file that contains information about the system configuration, such as the kernel parameters and the services that are started at boot time. It is not used to configure the filesystems that are mounted on the system.
E. None of the above is the correct answer.