What is the role of the launchd process in the startup of an OS X Mountain Lion computer?

A.
The kernel starts launchd, then launchd starts all the other processes involved in startup.

B.
The init process starts launchd, then launchd starts the items stored in the StartupItems folder.

C.
launchd starts the init process, then init starts all the other processes involved in startup.

D.
The init process starts launchd, then launchd starts the scripts stored in /etc/chron/.