Which three VMware-recommended best practices should an administrator follow before upgrading to vSphere
6.5? (Choose three.)
A.
Disconnect ESXi host from vCenter.
B.
VMware Tools are installed in the virtual machine.
C.
Ensure that the system hardware complies with ESXi requirements.
D.
Back up the host.
E.
Check the interoperability of any other software integrated with vSphere.
C,D,E is OK
https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.upgrade.doc/GUID-C8D42584-C272-4CA3-95C8-CE081B0489F5.html
“If your vSphere system includes VMware solutions or plug-ins, make sure they are compatible with the vCenter Server version that you are upgrading to.
Make sure that the system hardware complies with ESXi requirements.
Back up the host before performing an upgrade. If the upgrade fails, you can restore the host.”
C, D & E
(https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.upgrade.doc/GUID-C8D42584-C272-4CA3-95C8-CE081B0489F5.html)