You have three databases， FINDB， PAYDB and ADMINDB， located in Sydney， Tokyo and Singapore respectively. You want to perform administrative tasks which include starting up and shutting down the databases， creating and managing tablespaces and database users， and taking regular backups， for all of the three databases from London. Which component must be enabled and running on each host machine to achieve your objective？（）
- AOracle Management Agent
- BEnterprise Manager with Grid Control
- CEnterprise Manager with Database Control
- DOperating System Socket for incoming requests
- EReal Application Cluster （RAC） with three instances
- FEnterprise Manager with Generic Database Management