Which of the following best defines a virtual machine?

A.
A virtual instance of an operating system

B.
A piece of hardware that runs multiple operating system environments simultaneously

C.
A physical environment for multiple guests

D.
An environment that can be fully utilized while running legacy applications

Explanation:
A: A virtual machine is a virtual instance of an operating system. A virtual machine can also be called a guest, which runs in a host environment. The host
environmentusually an operating systemcan run multiple guests simultaneously. The virtual machines pool resources such as RAM, processors, and storage from
the host environment. This offers many benefits, including enhanced processing power utilization. Other benefits include the ability to run legacy applications. For
example, an organization may choose to run its legacy applications on an instance (virtual machine) of Windows XP long after it has rolled out Windows 7.
B is incorrect because a virtual machine is not a piece of hardware. A virtual machine is an instance of an operating system that runs on hardware. The host can run
multiple virtual machines. So, basically, you can have one computer running different operating systems at the same time. One benefit of this is consolidation. Using
virtual machines, you can consolidate the workloads of several under-utilized servers on to one host, thereby saving money on hardware and administrative
management tasks.
C is incorrect because virtual machines provide and work within software emulation. The host provides the resources, such as memory, processor, buses, RAM, and
storage for the virtual machines. The virtual machines share these resources but do not access them directly. The host environment, which is responsible for managing
the system resources, acts as an intermediary between the resources and the virtual machines.
D is incorrect because many legacy applications are not compatible with specific hardware and newer operating systems. Because of this, the application commonly
under-utilizes the server software and components. The virtual machines emulate an environment that allows legacy, and other, applications to fully use the resources
available to them. This is a reason to use a virtual machine, but the answer does not provide its definition.