An administrator is tasked with planning an upgrade of a VMware vSphere environment to version $7\mathrm{.}0.$ The platform consists of $80$ ESXi hosts, logically divided into $10$ clusters. The tasks will be completed by another operations team within the company.

The hardware is consistent, and a single embedded vCenter Server $6\mathrm{.}7$ appliance is managing the environment.

Which statement is true regarding a suitable upgrade approach? $($Choose the best answer.$)$

A$.$ The vCenter Server can be upgraded using a pre$-$configured customized JSON template.

B$.$ The ESXi hosts can only be upgraded using the Graphical User Interface Installer.

C$.$ Auto$-$deploy must be used to upgrade the large scale environment.

D$.$ A new Platform Services Controller must be deployed first.