Which of the Following Is True When a File System

Which of the following is true when a file system, which is neither listed in /etc/fstab nor known to system, is mounted manually?

A) systemd ignores any manual mounts which are not done using the systemctl mount command systemd ignores any manual mounts which are not done using the systemctl mount command
B) The command systemctl mountsync can be used to create a mount unit based on the existing mount The command systemctl mountsync can be used to create a mount unit based on the existing mount
C) systemd automatically generates a mount unit and monitors the mount point without changing it
D) Unless a systemd mount unit is created, systemd unmounts the file system after a short period of time
E) systemctl unmount must be used to remove the mount because system opens a file descriptor on the mount point systemctl unmount must be used to remove the mount because system opens a file descriptor on the mount point