To create a copy of a running virtual machine in the vSphere Client, what action must an administrator perform?

To create a copy of a running virtual machine in the vSphere Client, the administrator should perform the action of right-clicking on the VM and selecting the option to clone it as a virtual machine. This option allows for the exact duplication of the current state of the virtual machine, including its settings, configurations, and disk files, which can be particularly useful for various scenarios such as testing, scaling out applications, or creating backups.

When utilizing the cloning feature, the administrator can choose to either create a full clone, which operates independently from the original VM, or a linked clone that shares virtual disks with the original. This makes cloning a powerful and flexible option for managing virtual resources within a virtualized environment.

The other choices involve actions related to VM templates or converting existing templates into virtual machines, which do not pertain to copying a running VM directly. Thus, the most suitable and effective action for duplicating a running VM is indeed to clone it directly as a virtual machine.