An administrator is performing upgrades to ESXi 5.x from ESX 3.x and ESX 4.x hosts. What is true
about this procedure?

A.
A direct, in-place upgrade can be performed only on ESX 4.1 and later hosts.

B.
ESX 3.x hosts can be upgraded, but require an upgrade to 4.x before 5.x.

C.
A direct, in-place upgrade can be performed only on ESX 4.5 and later hosts.

D.
A direct, in-place upgrade can be performed only on ESX 3.5 and later hosts.

Explanation:

You must upgrade version 3.x ESX and ESXi hosts to ESX or ESXi version 4.x before you can
upgrade them to ESXi 5.1.x. See the vSphere 4.x upgrade documentation.
Alternatively, you might find it simpler and more cost effective to do a fresh installation of ESXi
5.1.x.