Which run levels should never be declared as the default run level when using SysV init? (Choose TWO correct answers.)

Run level 0 is defined as system halt - setting it as the default would cause the machine to shut down immediately upon reaching init, making the system inoperable.

Run level 1 is single-user/maintenance mode, which is restrictive but valid as a temporary default for recovery purposes.

Run level 3 is a normal multi-user mode without a graphical interface, which is a common and safe default run level.

Run level 5 is multi-user mode with a graphical interface, also a common and safe default run level.

Run level 6 is defined as system reboot - setting it as the default would cause an infinite reboot loop as the system restarts before fully initializing.