What happens after the instance is started?

Your database is down. You log in as the SYS user and issue this command:
SQL> STARTUP
What happens after the instance is started?

A.
Nothing else happens.

B.
The database is mounted but not opened.

C.
The database is mounted and finally opened.

D.
The database is opened and finally mounted.

Explanation:
http://docs.oracle.com/cd/E17781_01/server.112/e18804/startup.htm