Answer C is correct. To get a copy of all jobs, alerts, operators, and schedules, you back up the msdb database. SQL Server Agent maintains all this information within msdb. By backing up the system database, you also create emergency copies of other system metadata.
For more information, see the following sources:
Chapter 6, "Database Maintenance"
"Backing Up the model, msdb, and distribution Databases," http://msdn.microsoft.com/library/default.asp?url=/library/en-us/adminsql/ad_bkprst_4rlf.asp
Within MSDN Library, go to MSDN Home, MSDN Library, Servers and Enterprise Development, SQL Server, SQL Server 2005, Backing Up and Restoring Databases, Backing Up and Restoring System Databases, Backing Up the model, msdb, and distribution Databases.