Final answer:
Virtualization is the term used when someone uses software to run multiple operating systems.
Step-by-step explanation:
The correct answer to the question is c) Virtualization. Virtualization is the process of creating a virtual or simulated environment that can run multiple operating systems simultaneously using software. This allows users to switch between different operating systems without the need to restart the computer. Virtualization is commonly used in the field of computer science and is utilized for various purposes, such as running different operating systems for testing, software development, or for running legacy applications.