After upgrading an ESX host to vSphere 4.x from VI3, which of the following three achons should be taken (Choose Three)

A.
Configure ESX host networking

B.
Reconnect managed hosts to VMware vCenter

C.
Update any scripts that reference host sd devices

D.
Configure the ESX firewall

E.
Configure licensing

Explanation:
vSphere Upgrade Guide ESX 4.0 ESXi 4.0 vCenter Server 4.0 vSphere Client 4.0, page 79.
After you upgrade an ESX/ESXi host, consider the following:
right-clicking the host in the vCenter Server inventory and selecting Connect.
for 60 days. You must assign an upgraded license to your product within 60 days after the upgrade. Use the License Portal and the vSphere Client to configure licensing.
There is no requirement to restore files to the service console after an upgrade
Troubleshooting mode is not a valid mode for a vSphere host
It makes sense to verify virtual machine operation after an upgrade has taken pace.
Other correct options if mentioned in Question are:
1) verify virtual machine operation
2) restore vsphere webaccess on esx hosts
3) convert lun masking to claim rule format
4) re-enable 3rd party agents that get disabled by vihostupdated vsphere cli command