In virtualization, ___________ enables multiple operating systems to run concurrently on a single physical machine.

The correct option is "Hypervisor." A hypervisor, also known as a virtual machine monitor (VMM), allows multiple virtual machines (VMs) to run on a single physical machine by abstracting and managing the underlying hardware resources. It provides isolation, resource allocation, and control over the VMs, enabling different operating systems to coexist on the same hardware.