Virtualization is correct because it is the core technology that lets cloud providers operate multiple isolated workloads on the same physical machines.

Virtualization abstracts physical hardware using a hypervisor so that each virtual machine has its own virtual hardware and operating system. This abstraction provides strong isolation and independent allocation of CPU memory and storage, and it allows providers to run different operating systems on the same host while keeping workloads separated.

Multitenancy is incorrect because it describes a cloud design and business model where multiple customers share the same infrastructure. It is an important characteristic of cloud services and it is often enabled by Virtualization and other technologies, but it is not the underlying enabling technology itself.

Containerization is incorrect because containers provide process level isolation by sharing the host kernel with namespaces and control groups. Containers increase density and deployment speed, and they are complementary to Virtualization, but they do not by themselves create full hardware level isolation across multiple full operating system instances.

Resource pooling is incorrect because it is a cloud characteristic that describes sharing and dynamic allocation of resources across many customers. It is enabled by technologies such as Virtualization and management software, but it is an architectural principle rather than the specific core technology that creates isolated workloads.

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