A type 1 hypervisor OS, also known as a bare-metal hypervisor, is a software layer that runs directly on the hardware and allows multiple operating systems to run as virtual machines on the same host. This is the best choice for the test server because it provides the highest performance, isolation, and flexibility for testing different operating systems. A type 1 hypervisor OS can also support live migration, replication, and backup of virtual machines. A server OS is an operating system that is designed to run on a server, which is a computer that provides services to other computers on a network. A server OS may not support multiple operating systems or virtualization, and may have different hardware and software requirements than a test server. An embedded OS is an operating system that is embedded in a device, such as a smartphone, tablet, or smart TV. An embedded OS is usually optimized for a specific function and hardware, and may not support multiple operating systems or virtualization. A workstation OS is an operating system that is designed to run on a workstation, which is a high-end computer that is used for intensive tasks, such as graphics, video editing, or engineering. A workstation OS may support multiple operating systems or virtualization, but it may not have the same features and capabilities as a type 1 hypervisor OS, such as live migration, replication, and backup of virtual machines. Reference:
CompTIA IT Fundamentals (ITF+) Certification Guide, page 311
Introduction to Hyper-V on Windows 10