Which mount option must be used in the example / etc/ fstab entry below, to ensure that a specific filesystem is not mounted when the system is booted?

Which mount option must be used in the example / etc/ fstab entry below, to ensure that a specific filesystem is not mounted when the system is booted?

/dev/hdd /media/cdrom iso9660 _____________________,ro 0 0

Answer: noauto