The vSphere 4 Host Update Utility provides a graphical user interface for (Choose Two):

A.
upgrading ESX hosts in DRS/HA clusters

B.
upgrading standalone ESX/ESXi hosts

C.
performing a host compatibility check

D.
keeping guest operating systems patched

Explanation:
vSphere Host Update Utility
This tool is for upgrading ESX 3.x/ESXi 3.5 standalone hosts to ESX 4.0/ESXi 4.0 and
for patching ESXi 4.0 standalone hosts. A standalone host is an ESX/ESXi host that is
not managed in vCenter Server.
When you select a host to be upgraded, the tool performs an automated host
compatibility check as a preupgrade step.