Which virtual machine file type should an administrator select to copy a single hard disk from one datastore to another?

To copy a single hard disk from one datastore to another, the administrator should select the vmdk file type. The vmdk (Virtual Machine Disk) file is specifically designed to represent the virtual hard disk of a virtual machine. It contains the data and the operating system information necessary for the VM's operation.

When managing virtual machines in a VMware environment, the vmdk files are essential as they store the contents of the virtual disks. Copying the vmdk file allows the virtual machine to retain its data and configurations during the transfer to a different datastore.

In contrast, the other file types serve different purposes. The vmss file type is used for the suspended state of a virtual machine, allowing it to maintain its state when paused. The vswp file type is associated with swap files, which assist with memory management during VM operation. Lastly, the vmx file type is the configuration file for the virtual machine, containing settings and parameters, but it does not hold disk data.

Understanding the role of these file types is crucial for effective VMware administration, especially when it comes to managing and migrating virtual disks across datastores.