A vSphere administrator upgrades a version 5.1.0 vSphere Distributed Switch to version 5.5.0. Another vSphere administrator, unaware of this change, tries to add an ESXi version 5.1.0 host to the switch and fails. What is causing this addition of the ESXi host to fail?
A. The upgraded switch supports version 5.5 ESXi hosts only.
B. The upgraded switch must be set up for backwards compatibility.
C. The switch failed to upgrade properly.
D. A version 5.5 ESXi host must be added to the switch before the 5.1 host.