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.

Explanation:

You must install the Client Integration Plug-in before you deploy or upgrade the vCenter Server Appliance.
Reference: https://pubs.vmware.com/vsphere-60/index.jsp?topic=%2Fcom.vmware.vsphere.upgrade.doc%
2FGUID-CA16F78B-7890-4357-9760-AF8648806FE7.html