C - OK
For example, 100 servers may have one database each, with each database using 10% of hardware resources and 10% of an administrator's time. A team of DBAs must manage the SGA, database files, accounts, security, and so on of each database separately, while system administrators must maintain 100 different computers.
D - OK
Fewer database patches and upgrades
It is easier to apply a patch to one database than to 100 databases, and to upgrade one database than to upgrade 100 databases.
http://docs.oracle.com/database/121/CNCPT/cdbovrvw.htm#CNCPT89240