What action must be taken before upgrading the vCenter …

An administrator is upgrading a vCenter Server Appliance and wants to ensure that all the prerequisites are met.
What action must be taken before upgrading the vCenter Server Appliance?

A.
Install the Client Integration Plug-in.

B.
Install the database client.

C.
Install the ODBC connector.

D.
Install the Update Manager Plug-in.